提高PHP代码质量36计_PHP教程

1.不要使用相对路径

常常会看到: 

<ol class="dp-c"><li class="alt"><span><span class="keyword">require_once</span><span>(</span><span class="string">'../../lib/some_class.php'</span><span>); </span></span></li></ol>

该方法有很多缺点:

它首先查找指定的php包含路径, 然后查找当前目录.

因此会检查过多路径.

如果该脚本被另一目录的脚本包含, 它的基本目录变成了另一脚本所在的目录.

另一问题, 当定时任务运行该脚本, 它的上级目录可能就不是工作目录了.

因此最佳选择是使用绝对路径:

<ol class="dp-c">
<li class="alt"><span><span>define(</span><span class="string">'ROOT'</span><span> , </span><span class="string">'/var/www/project/'</span><span>);  </span></span></li>
<li>
<span class="keyword">require_once</span><span>(ROOT . </span><span class="string">'../../lib/some_class.php'</span><span>);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//rest of the code</span><span> </span>
</li>
</ol>

我们定义了一个绝对路径, 值被写死了. 我们还可以改进它. 路径 /var/www/project 也可能会改变, 那么我们每次都要改变它吗? 不是的, 我们可以使用__FILE__常量, 如: 

<ol class="dp-c">
<li class="alt"><span><span class="comment">//suppose your script is /var/www/project/index.php </span><span> </span></span></li>
<li>
<span class="comment">//Then __FILE__ will always have that full path. </span><span> </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>define(</span><span class="string">'ROOT'</span><span> , </span><span class="func">pathinfo</span><span>(</span><span class="keyword">__FILE__</span><span>, PATHINFO_DIRNAME));  </span>
</li>
<li class="alt">
<span class="keyword">require_once</span><span>(ROOT . </span><span class="string">'../../lib/some_class.php'</span><span>);  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//rest of the code</span><span> </span>
</li>
</ol>

现在, 无论你移到哪个目录, 如移到一个外网的服务器上, 代码无须更改便可正确运行.

2. 不要直接使用 require, include, include_once, required_once

可以在脚本头部引入多个文件, 像类库, 工具文件和助手函数等, 如: 

<ol class="dp-c">
<li class="alt"><span><span class="keyword">require_once</span><span>(</span><span class="string">'lib/Database.php'</span><span>);  </span></span></li>
<li>
<span class="keyword">require_once</span><span>(</span><span class="string">'lib/Mail.php'</span><span>);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="keyword">require_once</span><span>(</span><span class="string">'helpers/utitlity_functions.php'</span><span>); </span>
</li>
</ol>

这种用法相当原始. 应该更灵活点. 应编写个助手函数包含文件. 例如:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> load_class(</span><span class="vars">$class_name</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//path to the class file </span><span> </span>
</li>
<li>
<span>    </span><span class="vars">$path</span><span> = ROOT . </span><span class="string">'/lib/'</span><span> . </span><span class="vars">$class_name</span><span> . </span><span class="string">'.php'</span><span>);  </span>
</li>
<li class="alt">
<span>    </span><span class="keyword">require_once</span><span>( </span><span class="vars">$path</span><span> );  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>load_class(</span><span class="string">'Database'</span><span>);  </span>
</li>
<li class="alt">
<span>load_class(</span><span class="string">'Mail'</span><span>); </span>
</li>
</ol>

有什么不一样吗? 该代码更具可读性.

將来你可以按需扩展该函数, 如:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> load_class(</span><span class="vars">$class_name</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//path to the class file </span><span> </span>
</li>
<li>
<span>    </span><span class="vars">$path</span><span> = ROOT . </span><span class="string">'/lib/'</span><span> . </span><span class="vars">$class_name</span><span> . </span><span class="string">'.php'</span><span>);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">if</span><span>(</span><span class="func">file_exists</span><span>(</span><span class="vars">$path</span><span>))  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="keyword">require_once</span><span>( </span><span class="vars">$path</span><span> );  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span>} </span></li>
</ol>

还可做得更多:

为同样文件查找多个目录

能很容易的改变放置类文件的目录, 无须在代码各处一一修改

可使用类似的函数加载文件, 如html内容.

3. 为应用保留调试代码

在开发环境中, 我们打印数据库查询语句, 转存有问题的变量值, 而一旦问题解决, 我们注释或删除它们. 然而更好的做法是保留调试代码.

在开发环境中, 你可以:

<ol class="dp-c">
<li class="alt"><span><span>define(</span><span class="string">'ENVIRONMENT'</span><span> , </span><span class="string">'development'</span><span>);  </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">if</span><span>(! </span><span class="vars">$db</span><span>->query( </span><span class="vars">$query</span><span> )  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">if</span><span>(ENVIRONMENT == </span><span class="string">'development'</span><span>)  </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="func">echo</span><span> </span><span class="string">"$query failed"</span><span>;  </span>
</li>
<li><span>    }  </span></li>
<li class="alt">
<span>    </span><span class="keyword">else</span><span> </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="func">echo</span><span> </span><span class="string">"Database error. Please contact administrator"</span><span>;  </span>
</li>
<li><span>    }  </span></li>
<li class="alt"><span>} </span></li>
</ol>

在服务器中, 你可以:

<ol class="dp-c">
<li class="alt"><span><span>define(</span><span class="string">'ENVIRONMENT'</span><span> , </span><span class="string">'production'</span><span>);  </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">if</span><span>(! </span><span class="vars">$db</span><span>->query( </span><span class="vars">$query</span><span> )  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">if</span><span>(ENVIRONMENT == </span><span class="string">'development'</span><span>)  </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="func">echo</span><span> </span><span class="string">"$query failed"</span><span>;  </span>
</li>
<li><span>    }  </span></li>
<li class="alt">
<span>    </span><span class="keyword">else</span><span> </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="func">echo</span><span> </span><span class="string">"Database error. Please contact administrator"</span><span>;  </span>
</li>
<li><span>    }  </span></li>
<li class="alt"><span>} </span></li>
</ol>

4. 使用可跨平台的函数执行命令

system, exec, passthru, shell_exec 这4个函数可用于执行系统命令. 每个的行为都有细微差别. 问题在于, 当在共享主机中, 某些函数可能被选择性的禁用. 大多数新手趋于每次首先检查哪个函数可用, 然而再使用它.

更好的方案是封成函数一个可跨平台的函数. 

<ol class="dp-c">
<li class="alt"><span><span class="comment">/** </span> </span></li>
<li><span><span class="comment">    Method to execute a command in the terminal </span> </span></li>
<li class="alt"><span><span class="comment">    Uses : </span> </span></li>
<li><span> </span></li>
<li class="alt"><span><span class="comment">    1. system </span> </span></li>
<li><span><span class="comment">    2. passthru </span> </span></li>
<li class="alt"><span><span class="comment">    3. exec </span> </span></li>
<li><span><span class="comment">    4. shell_exec </span> </span></li>
<li class="alt"><span> </span></li>
<li><span><span class="comment">*/</span><span> </span></span></li>
<li class="alt">
<span class="keyword">function</span><span> terminal(</span><span class="vars">$command</span><span>)  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//system </span><span> </span>
</li>
<li>
<span>    </span><span class="keyword">if</span><span>(function_exists(</span><span class="string">'system'</span><span>))  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li><span>        ob_start();  </span></li>
<li class="alt">
<span>        system(</span><span class="vars">$command</span><span> , </span><span class="vars">$return_var</span><span>);  </span>
</li>
<li>
<span>        </span><span class="vars">$output</span><span> = ob_get_contents();  </span>
</li>
<li class="alt"><span>        ob_end_clean();  </span></li>
<li><span>    }  </span></li>
<li class="alt">
<span>    </span><span class="comment">//passthru </span><span> </span>
</li>
<li>
<span>    </span><span class="keyword">else</span><span> </span><span class="keyword">if</span><span>(function_exists(</span><span class="string">'passthru'</span><span>))  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li><span>        ob_start();  </span></li>
<li class="alt">
<span>        </span><span class="func">passthru</span><span>(</span><span class="vars">$command</span><span> , </span><span class="vars">$return_var</span><span>);  </span>
</li>
<li>
<span>        </span><span class="vars">$output</span><span> = ob_get_contents();  </span>
</li>
<li class="alt"><span>        ob_end_clean();  </span></li>
<li><span>    }  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="comment">//exec </span><span> </span>
</li>
<li class="alt">
<span>    </span><span class="keyword">else</span><span> </span><span class="keyword">if</span><span>(function_exists(</span><span class="string">'exec'</span><span>))  </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="func">exec</span><span>(</span><span class="vars">$command</span><span> , </span><span class="vars">$output</span><span> , </span><span class="vars">$return_var</span><span>);  </span>
</li>
<li>
<span>        </span><span class="vars">$output</span><span> = implode(</span><span class="string">"n"</span><span> , </span><span class="vars">$output</span><span>);  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="comment">//shell_exec </span><span> </span>
</li>
<li>
<span>    </span><span class="keyword">else</span><span> </span><span class="keyword">if</span><span>(function_exists(</span><span class="string">'shell_exec'</span><span>))  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="vars">$output</span><span> = shell_exec(</span><span class="vars">$command</span><span>) ;  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="keyword">else</span><span> </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="vars">$output</span><span> = </span><span class="string">'Command execution not possible on this system'</span><span>;  </span>
</li>
<li>
<span>        </span><span class="vars">$return_var</span><span> = 1;  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="keyword">return</span><span> </span><span class="keyword">array</span><span>(</span><span class="string">'output'</span><span> => </span><span class="vars">$output</span><span> , </span><span class="string">'status'</span><span> => </span><span class="vars">$return_var</span><span>);  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>terminal(</span><span class="string">'ls'</span><span>); </span>
</li>
</ol>

上面的函数將运行shell命令, 只要有一个系统函数可用, 这保持了代码的一致性. 

5. 灵活编写函数

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> add_to_cart(</span><span class="vars">$item_id</span><span> , </span><span class="vars">$qty</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$_SESSION</span><span>[</span><span class="string">'cart'</span><span>][</span><span class="string">'item_id'</span><span>] = </span><span class="vars">$qty</span><span>;  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>add_to_cart( </span><span class="string">'IPHONE3'</span><span> , 2 ); </span>
</li>
</ol>

使用上面的函数添加单个项目. 而当添加项列表的时候,你要创建另一个函数吗? 不用, 只要稍加留意不同类型的参数, 就会更灵活. 如:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> add_to_cart(</span><span class="vars">$item_id</span><span> , </span><span class="vars">$qty</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">if</span><span>(!</span><span class="func">is_array</span><span>(</span><span class="vars">$item_id</span><span>))  </span>
</li>
<li><span>    {  </span></li>
<li class="alt">
<span>        </span><span class="vars">$_SESSION</span><span>[</span><span class="string">'cart'</span><span>][</span><span class="string">'item_id'</span><span>] = </span><span class="vars">$qty</span><span>;  </span>
</li>
<li><span>    }  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">else</span><span> </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="keyword">foreach</span><span>(</span><span class="vars">$item_id</span><span> </span><span class="keyword">as</span><span> </span><span class="vars">$i_id</span><span> => </span><span class="vars">$qty</span><span>)  </span>
</li>
<li class="alt"><span>        {  </span></li>
<li>
<span>            </span><span class="vars">$_SESSION</span><span>[</span><span class="string">'cart'</span><span>][</span><span class="string">'i_id'</span><span>] = </span><span class="vars">$qty</span><span>;  </span>
</li>
<li class="alt"><span>        }  </span></li>
<li><span>    }  </span></li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt">
<span>add_to_cart( </span><span class="string">'IPHONE3'</span><span> , 2 );  </span>
</li>
<li>
<span>add_to_cart( </span><span class="keyword">array</span><span>(</span><span class="string">'IPHONE3'</span><span> => 2 , </span><span class="string">'IPAD'</span><span> => 5) ); </span>
</li>
</ol>

现在, 同个函数可以处理不同类型的输入参数了. 可以参照上面的例子重构你的多处代码, 使其更智能.

6. 有意忽略php关闭标签

我很想知道为什么这么多关于php建议的博客文章都没提到这点.

<ol class="dp-c">
<li class="alt"><span><span><?php  </span></span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">echo</span><span> </span><span class="string">"Hello"</span><span>;  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//Now dont close this tag</span><span> </span>
</li>
</ol>

这將节约你很多时间. 我们举个例子:

一个 super_class.php 文件

<ol class="dp-c">
<li class="alt"><span><span><?php  </span></span></span></li>
<li>
<span class="keyword">class</span><span> super_class  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="keyword">function</span><span> super_function()  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="comment">//super code </span><span> </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span>}  </span></li>
<li class="alt"><span>?>  </span></li>
<li>
<span class="comment">//super extra character after the closing tag</span><span> </span>
</li>
</ol>

index.php

<ol class="dp-c">
<li class="alt"><span><span class="keyword">require_once</span><span>(</span><span class="string">'super_class.php'</span><span>);  </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//echo an image or pdf , or set the cookies or session data</span><span> </span>
</li>
</ol>

这样, 你將会得到一个 Headers already send error. 为什么? 因为 “super extra character” 已经被输出了. 现在你得开始调试啦. 这会花费大量时间寻找 super extra 的位置.

因此, 养成省略关闭符的习惯:

<ol class="dp-c">
<li class="alt"><span><span><?php  </span></span></span></li>
<li>
<span class="keyword">class</span><span> super_class  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="keyword">function</span><span> super_function()  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="comment">//super code </span><span> </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//No closing tag</span><span> </span>
</li>
</ol>

这会更好. 

7. 在某地方收集所有输入, 一次输出给浏览器

这称为输出缓冲, 假如说你已在不同的函数输出内容:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> print_header()  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="func">echo</span><span> </span><span class="string">"<div>Site Log and Login links</div>"</span><span>;  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="keyword">function</span><span> print_footer()  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="func">echo</span><span> </span><span class="string">"<div>Site was made by me</div>"</span><span>;  </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt"><span>print_header();  </span></li>
<li>
<span class="keyword">for</span><span>(</span><span class="vars">$i</span><span> = 0 ; </span><span class="vars">$i</span><span> <span class="vars">$i</span><span>++)  </span></span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="func">echo</span><span> "I is : </span><span class="vars">$i</span><span> <br>';  </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span>print_footer(); </span></li>
</ol>

替代方案, 在某地方集中收集输出. 你可以存储在函数的局部变量中, 也可以使用ob_start和ob_end_clean. 如下:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> print_header()  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$o</span><span> = </span><span class="string">"<div>Site Log and Login links</div>"</span><span>;  </span>
</li>
<li>
<span>    </span><span class="keyword">return</span><span> </span><span class="vars">$o</span><span>;  </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">function</span><span> print_footer()  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$o</span><span> = </span><span class="string">"<div>Site was made by me</div>"</span><span>;  </span>
</li>
<li>
<span>    </span><span class="keyword">return</span><span> </span><span class="vars">$o</span><span>;  </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="func">echo</span><span> print_header();  </span>
</li>
<li>
<span class="keyword">for</span><span>(</span><span class="vars">$i</span><span> = 0 ; </span><span class="vars">$i</span><span> <span class="vars">$i</span><span>++)  </span></span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="func">echo</span><span> "I is : </span><span class="vars">$i</span><span> <br>';  </span>
</li>
<li class="alt"><span>}  </span></li>
<li>
<span class="func">echo</span><span> print_footer(); </span>
</li>
</ol>

为什么需要输出缓冲:

>>可以在发送给浏览器前更改输出. 如 str_replaces 函数或可能是 preg_replaces 或添加些监控/调试的html内容.

>>输出给浏览器的同时又做php的处理很糟糕. 你应该看到过有些站点的侧边栏或中间出现错误信息. 知道为什么会发生吗? 因为处理和输出混合了.

8. 发送正确的mime类型头信息, 如果输出非html内容的话.

输出一些xml.

<ol class="dp-c">
<li class="alt"><span><span class="vars">$xml</span><span> = </span><span class="string">'<?xml  version="1.0" encoding="utf-8" standalone="yes"?>'</span><span>;  </span></span></li>
<li>
<span class="vars">$xml</span><span> = "<response>  </response></span>
</li>
<li class="alt"><span>  <code>0</code>  </span></li>
<li><span>";  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Send xml data </span><span> </span>
</li>
<li class="alt">
<span class="func">echo</span><span> </span><span class="vars">$xml</span><span>; </span>
</li>
</ol>

工作得不错. 但需要一些改进.

<ol class="dp-c">
<li class="alt"><span><span class="vars">$xml</span><span> = </span><span class="string">'<?xml  version="1.0" encoding="utf-8" standalone="yes"?>'</span><span>;  </span></span></li>
<li>
<span class="vars">$xml</span><span> = "<response>  </response></span>
</li>
<li class="alt"><span>  <code>0</code>  </span></li>
<li><span>";  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Send xml data </span><span> </span>
</li>
<li class="alt">
<span>header(</span><span class="string">"content-type: text/xml"</span><span>);  </span>
</li>
<li>
<span class="func">echo</span><span> </span><span class="vars">$xml</span><span>; </span>
</li>
</ol>

注意header行. 该行告知浏览器发送的是xml类型的内容. 所以浏览器能正确的处理. 很多的javascript库也依赖头信息.

类似的有 javascript , css, jpg image, png image:

JavaScript

<ol class="dp-c">
<li class="alt"><span><span>header(</span><span class="string">"content-type: application/x-javascript"</span><span>);  </span></span></li>
<li>
<span class="func">echo</span><span> </span><span class="string">"var a = 10"</span><span>; </span>
</li>
</ol>

CSS

<ol class="dp-c">
<li class="alt"><span><span>header(</span><span class="string">"content-type: text/css"</span><span>);  </span></span></li>
<li>
<span class="func">echo</span><span> </span><span class="string">"#div id { background:#000; }"</span><span>; </span>
</li>
</ol>

9. 为mysql连接设置正确的字符编码

曾经遇到过在mysql表中设置了unicode/utf-8编码,  phpadmin也能正确显示, 但当你获取内容并在页面输出的时候,会出现乱码. 这里的问题出在mysql连接的字符编码.

<ol class="dp-c">
<li class="alt"><span><span class="comment">//Attempt to connect to database </span><span> </span></span></li>
<li>
<span class="vars">$c</span><span> = mysqli_connect(</span><span class="vars">$this</span><span>->host , </span><span class="vars">$this</span><span>->username, </span><span class="vars">$this</span><span>->password);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Check connection validity </span><span> </span>
</li>
<li class="alt">
<span class="keyword">if</span><span> (!</span><span class="vars">$c</span><span>)   </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">die</span><span> (</span><span class="string">"Could not connect to the database host: <br>"</span><span>. mysqli_connect_error());  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Set the character set of the connection </span><span> </span>
</li>
<li class="alt">
<span class="keyword">if</span><span>(!mysqli_set_charset ( </span><span class="vars">$c</span><span> , </span><span class="string">'UTF8'</span><span> ))  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">die</span><span>(</span><span class="string">'mysqli_set_charset() failed'</span><span>);  </span>
</li>
<li><span>} </span></li>
</ol>

一旦连接数据库, 最好设置连接的 characterset. 你的应用如果要支持多语言, 这么做是必须的.

10. 使用 htmlentities 设置正确的编码选项

php5.4前, 字符的默认编码是ISO-8859-1, 不能直接输出如À â等.

<ol class="dp-c"><li class="alt"><span><span class="vars">$value</span><span> = htmlentities(</span><span class="vars">$this</span><span>->value , ENT_QUOTES , CHARSET); </span></span></li></ol>

php5.4以后, 默认编码为UTF-8, 这將解决很多问题. 但如果你的应用是多语言的, 仍然要留意编码问题,.

11. 不要在应用中使用gzip压缩输出, 让apache处理

考虑过使用 ob_gzhandler 吗? 不要那样做. 毫无意义. php只应用来编写应用. 不应操心服务器和浏览器的数据传输优化问题.

使用apache的mod_gzip/mod_deflate 模块压缩内容.

12. 使用json_encode输出动态javascript内容

时常会用php输出动态javascript内容:

<ol class="dp-c">
<li class="alt"><span><span class="vars">$images</span><span> = </span><span class="keyword">array</span><span>(  </span></span></li>
<li>
<span> </span><span class="string">'myself.png'</span><span> , </span><span class="string">'friends.png'</span><span> , </span><span class="string">'colleagues.png'</span><span> </span>
</li>
<li class="alt"><span>);  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="vars">$js_code</span><span> = </span><span class="string">''</span><span>;  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">foreach</span><span>(</span><span class="vars">$images</span><span> </span><span class="keyword">as</span><span> </span><span class="vars">$image</span><span>)  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span class="vars">$js_code</span><span> .= </span><span class="string">"'$image' ,"</span><span>;  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="vars">$js_code</span><span> = </span><span class="string">'var images = ['</span><span> . </span><span class="vars">$js_code</span><span> . </span><span class="string">']; '</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="func">echo</span><span> </span><span class="vars">$js_code</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Output is var images = ['myself.png' ,'friends.png' ,'colleagues.png' ,];</span><span> </span>
</li>
</ol>

更聪明的做法, 使用 json_encode:

<ol class="dp-c">
<li class="alt"><span><span class="vars">$images</span><span> = </span><span class="keyword">array</span><span>(  </span></span></li>
<li>
<span> </span><span class="string">'myself.png'</span><span> , </span><span class="string">'friends.png'</span><span> , </span><span class="string">'colleagues.png'</span><span> </span>
</li>
<li class="alt"><span>);  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="vars">$js_code</span><span> = </span><span class="string">'var images = '</span><span> . json_encode(</span><span class="vars">$images</span><span>);  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="func">echo</span><span> </span><span class="vars">$js_code</span><span>;  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//Output is : var images = ["myself.png","friends.png","colleagues.png"]</span><span> </span>
</li>
</ol>

优雅乎?

13. 写文件前, 检查目录写权限

写或保存文件前, 确保目录是可写的, 假如不可写, 输出错误信息. 这会节约你很多调试时间. linux系统中, 需要处理权限, 目录权限不当会导致很多很多的问题, 文件也有可能无法读取等等.

确保你的应用足够智能, 输出某些重要信息.

<ol class="dp-c">
<li class="alt"><span><span class="vars">$contents</span><span> = </span><span class="string">"All the content"</span><span>;  </span></span></li>
<li>
<span class="vars">$file_path</span><span> = </span><span class="string">"/var/www/project/content.txt"</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="func">file_put_contents</span><span>(</span><span class="vars">$file_path</span><span> , </span><span class="vars">$contents</span><span>); </span>
</li>
</ol>

这大体上正确. 但有些间接的问题. file_put_contents 可能会由于几个原因失败:

>>父目录不存在

>>目录存在, 但不可写

>>文件被写锁住?

所以写文件前做明确的检查更好.

<ol class="dp-c">
<li class="alt"><span><span class="vars">$contents</span><span> = </span><span class="string">"All the content"</span><span>;  </span></span></li>
<li>
<span class="vars">$dir</span><span> = </span><span class="string">'/var/www/project'</span><span>;  </span>
</li>
<li class="alt">
<span class="vars">$file_path</span><span> = </span><span class="vars">$dir</span><span> . </span><span class="string">"/content.txt"</span><span>;  </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">if</span><span>(</span><span class="func">is_writable</span><span>(</span><span class="vars">$dir</span><span>))  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="func">file_put_contents</span><span>(</span><span class="vars">$file_path</span><span> , </span><span class="vars">$contents</span><span>);  </span>
</li>
<li><span>}  </span></li>
<li class="alt">
<span class="keyword">else</span><span> </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">die</span><span>(</span><span class="string">"Directory $dir is not writable, or does not exist. Please check"</span><span>);  </span>
</li>
<li><span>} </span></li>
</ol>

这么做后, 你会得到一个文件在何处写及为什么失败的明确信息.

14. 更改应用创建的文件权限

在 linux环境中, 权限问题可能会浪费你很多时间. 从今往后, 无论何时, 当你创建一些文件后, 确保使用chmod设置正确权限. 否则的话, 可能文件先是由"php"用户创建, 但你用其它的用户登录工作, 系统將会拒绝访问或打开文件, 你不得不奋力获取root权限,  更改文件的权限等等.

<ol class="dp-c">
<li class="alt"><span><span class="comment">// Read and write for owner, read for everybody else </span><span> </span></span></li>
<li>
<span class="func">chmod</span><span>(</span><span class="string">"/somedir/somefile"</span><span>, 0644);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">// Everything for owner, read and execute for others </span><span> </span>
</li>
<li class="alt">
<span class="func">chmod</span><span>(</span><span class="string">"/somedir/somefile"</span><span>, 0755); </span>
</li>
</ol>

15. 不要依赖submit按钮值来检查表单提交行为

<ol class="dp-c">
<li class="alt"><span><span class="keyword">if</span><span>(</span><span class="vars">$_POST</span><span>[</span><span class="string">'submit'</span><span>] == </span><span class="string">'Save'</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//Save the things </span><span> </span>
</li>
<li><span>} </span></li>
</ol>

上面大多数情况正确, 除了应用是多语言的. 'Save' 可能代表其它含义. 你怎么区分它们呢. 因此, 不要依赖于submit按钮的值.

<ol class="dp-c">
<li class="alt"><span><span class="keyword">if</span><span>( </span><span class="vars">$_SERVER</span><span>[</span><span class="string">'REQUEST_METHOD'</span><span>] == </span><span class="string">'POST'</span><span> </span><span class="keyword">and</span><span> isset(</span><span class="vars">$_POST</span><span>[</span><span class="string">'submit'</span><span>]) )  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//Save the things </span><span> </span>
</li>
<li><span>} </span></li>
</ol>

现在你从submit按钮值中解脱出来了.

16. 为函数内总具有相同值的变量定义成静态变量

<ol class="dp-c">
<li class="alt"><span><span class="comment">//Delay for some time </span><span> </span></span></li>
<li>
<span class="keyword">function</span><span> delay()  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="vars">$sync_delay</span><span> = get_option(</span><span class="string">'sync_delay'</span><span>);  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="func">echo</span><span> </span><span class="string">"<br>Delaying for $sync_delay seconds..."</span><span>;  </span>
</li>
<li class="alt">
<span>    sleep(</span><span class="vars">$sync_delay</span><span>);  </span>
</li>
<li>
<span>    </span><span class="func">echo</span><span> </span><span class="string">"Done <br>"</span><span>;  </span>
</li>
<li class="alt"><span>} </span></li>
</ol>

用静态变量取代:

<ol class="dp-c">
<li class="alt"><span><span class="comment">//Delay for some time </span><span> </span></span></li>
<li>
<span class="keyword">function</span><span> delay()  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="keyword">static</span><span> </span><span class="vars">$sync_delay</span><span> = null;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">if</span><span>(</span><span class="vars">$sync_delay</span><span> == null)  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>    </span><span class="vars">$sync_delay</span><span> = get_option(</span><span class="string">'sync_delay'</span><span>);  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="func">echo</span><span> </span><span class="string">"<br>Delaying for $sync_delay seconds..."</span><span>;  </span>
</li>
<li>
<span>    sleep(</span><span class="vars">$sync_delay</span><span>);  </span>
</li>
<li class="alt">
<span>    </span><span class="func">echo</span><span> </span><span class="string">"Done <br>"</span><span>;  </span>
</li>
<li><span>} </span></li>
</ol>

17. 不要直接使用 $_SESSION 变量

<ol class="dp-c">
<li class="alt"><span><span class="vars">$_SESSION</span><span>[</span><span class="string">'username'</span><span>] = </span><span class="vars">$username</span><span>;  </span></span></li>
<li>
<span class="vars">$username</span><span> = </span><span class="vars">$_SESSION</span><span>[</span><span class="string">'username'</span><span>]; </span>
</li>
</ol>

这会导致某些问题. 如果在同个域名中运行了多个应用, session 变量可能会冲突. 两个不同的应用可能使用同一个session key. 例如, 一个前端门户, 和一个后台管理系统使用同一域名.

从现在开始, 使用应用相关的key和一个包装函数:

<ol class="dp-c">
<li class="alt"><span><span>define(</span><span class="string">'APP_ID'</span><span> , </span><span class="string">'abc_corp_ecommerce'</span><span>);  </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//Function to get a session variable </span><span> </span>
</li>
<li>
<span class="keyword">function</span><span> session_get(</span><span class="vars">$key</span><span>)  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="vars">$k</span><span> = APP_ID . </span><span class="string">'.'</span><span> . </span><span class="vars">$key</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">if</span><span>(isset(</span><span class="vars">$_SESSION</span><span>[</span><span class="vars">$k</span><span>]))  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li>
<span>        </span><span class="keyword">return</span><span> </span><span class="vars">$_SESSION</span><span>[</span><span class="vars">$k</span><span>];  </span>
</li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="keyword">return</span><span> false;  </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="comment">//Function set the session variable </span><span> </span>
</li>
<li class="alt">
<span class="keyword">function</span><span> session_set(</span><span class="vars">$key</span><span> , </span><span class="vars">$value</span><span>)  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$k</span><span> = APP_ID . </span><span class="string">'.'</span><span> . </span><span class="vars">$key</span><span>;  </span>
</li>
<li>
<span>    </span><span class="vars">$_SESSION</span><span>[</span><span class="vars">$k</span><span>] = </span><span class="vars">$value</span><span>;  </span>
</li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">return</span><span> true;  </span>
</li>
<li class="alt"><span>} </span></li>
</ol>

18. 將工具函数封装到类中

假如你在某文件中定义了很多工具函数:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">function</span><span> utility_a()  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//This function does a utility thing like string processing </span><span> </span>
</li>
<li><span>}  </span></li>
<li class="alt"><span> </span></li>
<li>
<span class="keyword">function</span><span> utility_b()  </span>
</li>
<li class="alt"><span>{  </span></li>
<li>
<span>    </span><span class="comment">//This function does nother utility thing like database processing </span><span> </span>
</li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="keyword">function</span><span> utility_c()  </span>
</li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="comment">//This function is ... </span><span> </span>
</li>
<li><span>} </span></li>
</ol>

这些函数的使用分散到应用各处. 你可能想將他们封装到某个类中:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">class</span><span> Utility  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> utility_a()  </span>
</li>
<li><span>    {  </span></li>
<li class="alt"><span> </span></li>
<li><span>    }  </span></li>
<li class="alt"><span> </span></li>
<li>
<span>    </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> utility_b()  </span>
</li>
<li class="alt"><span>    {  </span></li>
<li><span> </span></li>
<li class="alt"><span>    }  </span></li>
<li><span> </span></li>
<li class="alt">
<span>    </span><span class="keyword">public</span><span> </span><span class="keyword">static</span><span> </span><span class="keyword">function</span><span> utility_c()  </span>
</li>
<li><span>    {  </span></li>
<li class="alt"><span> </span></li>
<li><span>    }  </span></li>
<li class="alt"><span>}  </span></li>
<li><span> </span></li>
<li class="alt">
<span class="comment">//and call them as  </span><span> </span>
</li>
<li><span> </span></li>
<li class="alt">
<span class="vars">$a</span><span> = Utility::utility_a();  </span>
</li>
<li>
<span class="vars">$b</span><span> = Utility::utility_b(); </span>
</li>
</ol>

显而易见的好处是, 如果php内建有同名的函数, 这样可以避免冲突.

另一种看法是, 你可以在同个应用中为同个类维护多个版本, 而不导致冲突. 这是封装的基本好处, 无它.

19. Bunch of silly tips 

>>使用echo取代print

>>使用str_replace取代preg_replace, 除非你绝对需要

>>不要使用 short tag

>>简单字符串用单引号取代双引号

>>head重定向后记得使用exit

>>不要在循环中调用函数

>>isset比strlen快

>>始中如一的格式化代码

>>不要删除循环或者if-else的括号

不要这样写代码:

<ol class="dp-c"><li class="alt"><span><span><span><span class="string">"color:#333333;font-family:''Helvetica, Arial, sans-serif'';"</span><span>></span><span class="keyword">if</span><span>(</span><span class="vars">$a</span><span> == true) </span><span class="vars">$a_count</span><span>++;</span> </span></span></span></li></ol>

这绝对WASTE.

写成:

<ol class="dp-c">
<li class="alt"><span><span><span><span class="string">"color:#333333;font-family:''Helvetica, Arial, sans-serif'';"</span><span>></span><span class="keyword">if</span><span>(</span><span class="vars">$a</span><span> == true)  </span></span></span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$a_count</span><span>++;  </span>
</li>
<li>
<span>}</span> </li>
</ol>

不要尝试省略一些语法来缩短代码. 而是让你的逻辑简短.

>>使用有高亮语法显示的文本编辑器. 高亮语法能让你减少错误.

20. 使用array_map快速处理数组

比如说你想 trim 数组中的所有元素. 新手可能会:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">foreach</span><span>(</span><span class="vars">$arr</span><span> </span><span class="keyword">as</span><span> </span><span class="vars">$c</span><span> => </span><span class="vars">$v</span><span>)  </span></span></li>
<li><span>{  </span></li>
<li class="alt">
<span>    </span><span class="vars">$arr</span><span>[</span><span class="vars">$c</span><span>] = trim(</span><span class="vars">$v</span><span>);  </span>
</li>
<li><span>} </span></li>
</ol>

但使用 array_map 更简单:

<ol class="dp-c"><li class="alt"><span><span class="vars">$arr</span><span> = </span><span class="func">array_map</span><span>(</span><span class="string">'trim'</span><span> , </span><span class="vars">$arr</span><span>); </span></span></li></ol>

这会为$arr数组的每个元素都申请调用trim. 另一个类似的函数是 array_walk. 请查阅文档学习更多技巧.

21. 使用 php filter 验证数据

你肯定曾使用过正则表达式验证 email , ip地址等. 是的,每个人都这么使用. 现在, 我们想做不同的尝试, 称为filter.

php的filter扩展提供了简单的方式验证和检查输入.

22. 强制类型检查

<ol class="dp-c">
<li class="alt"><span><span class="vars">$amount</span><span> = </span><span class="func">intval</span><span>( </span><span class="vars">$_GET</span><span>[</span><span class="string">'amount'</span><span>] );  </span></span></li>
<li>
<span class="vars">$rate</span><span> = (int) </span><span class="vars">$_GET</span><span>[</span><span class="string">'rate'</span><span>]; </span>
</li>
</ol>

这是个好习惯.

23. 如果需要,使用profiler如xdebug

如果你使用php开发大型的应用, php承担了很多运算量, 速度会是一个很重要的指标. 使用profile帮助优化代码. 可使用

xdebug和webgrid.

24. 小心处理大数组

对于大的数组和字符串, 必须小心处理. 常见错误是发生数组拷贝导致内存溢出,抛出Fat

<ol class="dp-c">
<li class="alt"><span><span class="vars">$db_records_in_array_format</span><span>; </span><span class="comment">//This is a big array holding 1000 rows from a table each having 20 columns , every row is atleast 100 bytes , so total 1000 * 20 * 100 = 2MB </span><span> </span></span></li>
<li><span> </span></li>
<li class="alt">
<span class="vars">$cc</span><span> = </span><span class="vars">$db_records_in_array_format</span><span>; </span><span class="comment">//2MB more </span><span> </span>
</li>
<li><span> </span></li>
<li class="alt">
<span>some_function(</span><span class="vars">$cc</span><span>); </span><span class="comment">//Another 2MB ?</span><span> </span>
</li>
</ol>

当导入或导出csv文件时, 常常会这么做.

不要认为上面的代码会经常因内存限制导致脚本崩溃. 对于小的变量是没问题的, 但处理大数组的时候就必须避免.

确保通过引用传递, 或存储在类变量中:

<ol class="dp-c">
<li class="alt"><span><span class="vars">$a</span><span> = get_large_array();  </span></span></li>
<li>
<span>pass_to_function(&</span><span class="vars">$a</span><span>); </span>
</li>
</ol>

这么做后,向函数传递变量引用(而不是拷贝数组). 查看

http://www.bkjia.com/PHPjc/445702.htmlwww.bkjia.comtruehttp://www.bkjia.com/PHPjc/445702.htmlTechArticle1.不要使用相对路径 常常会看到: require_once ( '../../lib/some_class.php' ); 该方法有很多缺点: 它首先查找指定的php包含路径, 然后查找当前目录...