PHP skills: 50 practical tips for high-quality PHP code (Part 1)

50 practical tips for high-quality PHP code, I hope you like it.

1. Don’t use relative paths
You often see:

require_once('../../lib/some_class.php');

This method has many shortcomings: It first looks for the specified php Contains the path and then looks for the current directory. So too many paths are checked. If the script is included by a script in another directory, its base directory becomes the directory where the other script is located.

Another problem, when the scheduled task runs the script, its parent directory may not be the working directory. Directory. So the best choice is to use an absolute path:

view sourceprint?
 define('ROOT' , '/var/www/project/');
 require_once(ROOT . '../../lib/some_class.php');
 //rest of the code

We have defined an absolute path, and the value is hard-coded. We can also improve it. The path /var/www/project may also change, then Do we have to change it every time? No, we can use the __FILE__ constant, such as:

//suppose your script is /var/www/project/index.php
 //Then __FILE__ will always have that full path.
 define('ROOT' , pathinfo(__FILE__, PATHINFO_DIRNAME));
 require_once(ROOT . '../../lib/some_class.php');
 //rest of the code

Now, no matter which directory you move to, such as moving to an external server, The code does not need to be changed to run correctly.

2. Do not use require, include, include_once, required_once directly
You can introduce multiple files at the head of the script, such as class libraries and tools Files and helper functions, such as:

require_once('lib/Database.php');
 require_once('lib/Mail.php');
 require_once('helpers/utitlity_functions.php');

This usage is quite primitive. It should be more flexible. A helper function should be written to include files. For example:

function load_class($class_name)
 {
 //path to the class file
 $path = ROOT . '/lib/' . $class_name . '.php');
 require_once( $path );
 }
 load_class('Database');
 load_class('Mail');

What's wrong with that? Is it the same? The code is more readable. In the future, you can extend this function as needed, such as:

function load_class($class_name)
 {
 //path to the class file
 $path = ROOT . '/lib/' . $class_name . '.php');
 if(file_exists($path))
 {
 require_once( $path );
 }
 }

You can also do more: find multiple directories for the same file. The directory where class files are placed can be easily changed without having to modify them one by one in the code. Similar functions can be used to load files, such as html content.

3. Keep debugging code for the application
In the development environment, we print database query statements and dump problematic ones Variable values, and once the problem is solved, we comment or delete them. However, it is better to keep the debug code. In the development environment, you can:

define('ENVIRONMENT' , 'development');
 if(! $db->query( $query )
 {
 if(ENVIRONMENT == 'development')
 {
 echo "$query failed";
 }
 else
 {
 echo "Database error. Please contact administrator";
 }
 }

In the server, you can:

define('ENVIRONMENT' , 'production');
 if(! $db->query( $query )
 {
 if(ENVIRONMENT == 'development')
 {
 echo "$query failed";
 }
 else
 {
 echo "Database error. Please contact administrator";
 }
 }

4. Use cross-platform functions to execute commands
System, exec, passthru, shell_exec These 4 functions can be used to execute system commands. The behavior of each one is slightly different. The problem is that when in shared hosting, some functions may be selectively disabled. Most newbies The tendency is to first check which function is available each time before using it. A better solution is to encapsulate the function into a cross-platform function.

/**
 Method to execute a command in the terminal
 Uses :
 1. system
 2. passthru
 3. exec
 4. shell_exec
 */
 function terminal($command)
 {
 //system
 if(function_exists('system'))
 {
 ob_start();
 system($command , $return_var);
 $output = ob_get_contents();
 ob_end_clean();
 }
 //passthru
 else if(function_exists('passthru'))
 {
 ob_start();
 passthru($command , $return_var);
 $output = ob_get_contents();
 ob_end_clean();
 }
 //exec
 else if(function_exists('exec'))
 {
 exec($command , $output , $return_var);
 $output = implode("\n" , $output);
 }
 //shell_exec
 else if(function_exists('shell_exec'))
 {
 $output = shell_exec($command) ;
 }
 else
 {
 $output = 'Command execution not possible on this system';
 $return_var = 1;
 }
return array('output' => $output , 'status' => $return_var);
 }
 terminal('ls');

The above function will run the shell command as long as there is a system function available, which maintains the consistency of the code.

5. Write functions flexibly

function add_to_cart($item_id , $qty)
  
{
 $_SESSION['cart']['item_id'] = $qty;
 }
add_to_cart( 'IPHONE3' , 2 );

Use the above function to add a single item. When adding a list of items, do you want to create another function? No, just If you pay a little attention to different types of parameters, you will be more flexible. For example:

function add_to_cart($item_id , $qty)
 {
 if(!is_array($item_id))
 {
 $_SESSION['cart']['item_id'] = $qty;
 }
 else
 {
 foreach($item_id as $i_id => $qty)
 {
 $_SESSION['cart']['i_id'] = $qty;
 }
 }
 }
 add_to_cart( 'IPHONE3' , 2 );
 add_to_cart( array('IPHONE3' => 2 , 'IPAD' => 5) );

Now, the same function can handle different types of input parameters. You can refactor multiple parts of your code by referring to the above example. , to make it smarter.

6. Intentionally ignore php closing tags
I’d love to know why so many blog posts about php advice don’t mention this.

<?php
 echo "Hello";
 //Now dont close this tag

This will save you a lot of time. Let’s give an example:
A super_class.php file

 //super extra character after the closing tag
index.php

require_once('super_class.php');
 //echo an image or pdf , or set the cookies or session data

In this way, you will get a Headers already send error . Why? Because the "super extra character" has been output. Now you have to start debugging. This will take a lot of time to find the location of the super extra. Therefore, get into the habit of omitting the closing character:

<?php
 class super_class
 {
 function super_function()
 {
 //super code
 }
 }
 //No closing tag

This will be better.

7. Collect all input somewhere and output it to the browser at once
This is called output buffering, let's say you have output in different functions:

function print_header()
 {
 echo "Site Log and Login links";
 }
 function print_footer()
 {
 echo "Site was made by me";
 }
 print_header();
 for($i = 0 ; $i < 100; $i++)
 {
 echo "I is : $i &#39;;
 }
print_footer();

Alternatively, collect the output centrally somewhere. You can store it in a function In local variables, you can also use ob_start and ob_end_clean. As follows:

function print_header()
 {
 $o = "Site Log and Login links";
 return $o;
 }
function print_footer()
 {
 $o = "Site was made by me";
 return $o;
 }
echo print_header();
 for($i = 0 ; $i < 100; $i++)
 {
 echo "I is : $i &#39;;
 }
 echo print_footer();

Why output buffering is needed:
>> You can change the output before sending it to the browser. Such as str_replaces The function may be preg_replaces or add some monitoring/debugging html content.
>>It is very bad to output to the browser and do PHP processing at the same time. You should have seen the sidebar or middle of some sites Error message. Do you know why it happens? Because processing and output are mixed.

8. Send the correct mime type header information, if non-html content is output.
Output some xml.

$xml = '';
 $xml = "0
 ";
//Send xml data
 echo $xml;

works well. But needs some improvement.

$xml = '';
 $xml = "0
 ";
 //Send xml data
 header("content-type: text/xml");
 echo $xml;

Pay attention to the header line. This line tells the browser that what is being sent is xml type content. So the browser can process it correctly. Many javascript libraries also rely on header information.
Similar ones include javascript, css, jpg image, png image:

JavaScript
header("content-type: application/x-javascript");
 echo "var a = 10";
 CSS
header("content-type: text/css");
 echo "#p id { background:#000; }";

9. Set the correct character encoding for mysql connection
I once encountered the unicode/utf-8 encoding set in the mysql table, and phpadmin can display it correctly, but when you get the content and output it on the page , there will be garbled characters. The problem here lies in the character encoding of the mysql connection.

//Attempt to connect to database
 $c = mysqli_connect($this->host , $this->username, $this->password);
 //Check connection validity
 if (!$c)
 {
 die ("Could not connect to the database host: ". mysqli_connect_error());
 }
 //Set the character set of the connection
if(!mysqli_set_charset ( $c , 'UTF8' ))
 {
 die('mysqli_set_charset() failed');
 }

Once connected to the database, it is best to set the connected characterset. If your application wants to support multiple languages, do this It is necessary.

10. Use htmlentities to set the correct encoding options
Before php5.4, the default encoding of characters is ISO-8859-1, which cannot be directly output such as À âWait.

$value = htmlentities($this->value , ENT_QUOTES , CHARSET);

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:

$images = array(
 'myself.png' , 'friends.png' , 'colleagues.png'
 );
$js_code = '';
foreach($images as $image)
{
$js_code .= "'$image' ,";
}
$js_code = 'var images = [' . $js_code . ']; ';
echo $js_code;
//Output is var images = ['myself.png' ,'friends.png' ,'colleagues.png' ,];
  
更聪明的做法, 使用 json_encode:
  
$images = array(
 'myself.png' , 'friends.png' , 'colleagues.png'
 );
$js_code = 'var images = ' . json_encode($images);
 echo $js_code;
//Output is : var images = ["myself.png","friends.png","colleagues.png"]

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.

$contents = "All the content";
$file_path = "/var/www/project/content.txt";
 file_put_contents($file_path , $contents);

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.

$contents = "All the content";
 $dir = '/var/www/project';
 $file_path = $dir . "/content.txt";
 if(is_writable($dir))
 {
 file_put_contents($file_path , $contents);
 }
 else
 {
 die("Directory $dir is not writable, or does not exist. Please check");
 }

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.

// Read and write for owner, read for everybody else
 chmod("/somedir/somefile", 0644);
 // Everything for owner, read and execute for others
 chmod("/somedir/somefile", 0755);

15. 不要依赖submit按钮值来检查表单提交行为

if($_POST['submit'] == 'Save')
 {
 //Save the things
 }

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.

if( $_SERVER['REQUEST_METHOD'] == 'POST' and isset($_POST['submit']) )
 {
 //Save the things
 }

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

//Delay for some time
 function delay()
 {
 $sync_delay = get_option('sync_delay');
 echo "Delaying for $sync_delay seconds...";
 sleep($sync_delay);
 echo "Done ";
 }

用静态变量取代:

//Delay for some time
 function delay()
 {
 static $sync_delay = null;
 if($sync_delay == null)
 {
 $sync_delay = get_option('sync_delay');
 }
 echo "Delaying for $sync_delay seconds...";
 sleep($sync_delay);
 echo "Done ";
 }

17. 不要直接使用 $_SESSION 变量
某些简单例子:

$_SESSION['username'] = $username;
 $username = $_SESSION['username'];

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:

define('APP_ID' , 'abc_corp_ecommerce');
 //Function to get a session variable
 function session_get($key)
 {
 $k = APP_ID . '.' . $key;
 if(isset($_SESSION[$k]))
 {
 return $_SESSION[$k];
 }
 return false;
 }
 //Function set the session variable
 function session_set($key , $value)
 {
 $k = APP_ID . '.' . $key;
 $_SESSION[$k] = $value;
 return true;
 }

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:

function utility_a()
 {
 //This function does a utility thing like string processing
 }
function utility_b()
 {
 //This function does nother utility thing like database processing
 }
 function utility_c()
 {
 //This function is ...
 }

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:

class Utility
 {
public static function utility_a()
{
}
public static function utility_b()
 {
 }
public static function utility_c()
 {
 }
 }
//and call them as
 $a = Utility::utility_a();
 $b = Utility::utility_b();

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:

if($a == true) $a_count++;

这绝对WASTE。写成:

if($a == true)
 {
 $a_count++;
 }

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:

foreach($arr as $c => $v)
 {
 $arr[$c] = trim($v);
 }

但使用 array_map 更简单:

$arr = array_map('trim' , $arr);

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

$amount = intval( $_GET['amount'] );
$rate = (int) $_GET['rate'];

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Fatal Error of Memory size 信息:

$db_records_in_array_format; //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
$cc = $db_records_in_array_format; //2MB more
some_function($cc); //Another 2MB ?

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:

$a = get_large_array();
 pass_to_function(&$a);

这么做后, 向函数传递变量引用(而不是拷贝数组). 查看文档.

class A
 {
 function first()
 {
 $this->a = get_large_array();
 $this->pass_to_function();
 }
 function pass_to_function()
 {
 //process $this->a
 }
 }

尽快的 unset 它们, 让内存得以释放,减轻脚本负担.

25. 由始至终使用单一数据库连接
确保你的脚本由始至终都使用单一的数据库连接. 在开始处正确的打开连接, 使用它直到结束, 最后关闭它. 不要像下面这样在函数中打开连接:

function add_to_cart()
 {
$db = new Database();
 $db->query("INSERT INTO cart .....");
 }
 function empty_cart()
 {
$db = new Database();
 $db->query("DELETE FROM cart .....");
 }

使用多个连接是个糟糕的, 它们会拖慢应用, 因为创建连接需要时间和占用内存。特定情况使用单例模式, 如数据库连接.。

这个秘籍是不是很精彩，相信一定对大家学习php程序设计有所帮助。

相关文章：

php技巧篇：高质量php代码的50个实用技巧（下）