PHP Basics Introduction to PHP Programming Statements_PHP Tutorial

The following introduces the programming statements in the PHP programming language.

1 Simple statement

Each line contains at most one statement, for example:

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span class="vars">$argv</span><span>++; </span><span class="comment">// 正确的 </span><span> </span></span></li>
<li>
<span class="vars">$argc</span><span>--; </span><span class="comment">// 正确的 </span><span> </span>
</li>
<li class="alt">
<span class="vars">$argv</span><span>++; </span><span class="vars">$argc</span><span>--; </span><span class="comment">// 错误的</span><span> </span>
</li>
</ol>

2 Compound statement

A compound statement is a sequence of statements contained in curly brackets, in the form of "{ statement}". For example, the following paragraphs.

• The enclosed statement should be indented one level compared to the compound statement
• The left brace "{" should be located at the end of the line starting with the compound statement; the closing brace " }" should start on a new line and be aligned with the first line of the compound statement.
• Braces can be used on all statements, including single statements, as long as they are part of a control structure such as if-else or for. This makes it easy to add statements without worrying about introducing bugs due to forgetting to add parentheses

3 Return statement

A return statement with a return value does not use parentheses "()" unless they somehow make the return value more visible. For example:

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">return</span><span>;  </span></span></li>
<li>
<span class="keyword">return</span><span> myDisk.size();  </span>
</li>
<li class="alt">
<span class="keyword">return</span><span> (</span><span class="vars">$size</span><span> ? </span><span class="vars">$size</span><span> : </span><span class="vars">$defaultSize</span><span>); </span>
</li>
</ol>

4 if and else statements

if-else statements should have the following format:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">if</span><span> (condition){ </span><span class="comment">/* 进行操作的条件 */</span><span> </span></span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>}  </span></li>
<li>
<span class="keyword">if</span><span> (condition) {</span><span class="comment">/*进行操作的条件. */</span><span> </span>
</li>
<li class="alt"><span>statements;  </span></li>
<li>
<span>} </span><span class="keyword">else</span><span> {</span><span class="comment">/*进行操作的条件*/</span><span> </span>
</li>
<li class="alt"><span>statements;  </span></li>
<li><span>}  </span></li>
<li class="alt">
<span class="keyword">if</span><span> (condition) {</span><span class="comment">/*进行操作的条件*/</span><span> </span>
</li>
<li><span>statements;  </span></li>
<li class="alt">
<span>} </span><span class="keyword">else</span><span> </span><span class="keyword">if</span><span> (condition) {</span><span class="comment">/*进行操作的条件 */</span><span> </span>
</li>
<li><span>statements;  </span></li>
<li class="alt">
<span>} </span><span class="keyword">else</span><span>{</span><span class="comment">/*进行操作的条件*/</span><span> </span>
</li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

Note: if statements are always enclosed in "{" and "}" to avoid using the following error-prone formats:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">if</span><span> (condition) </span><span class="comment">//避免这种写法，他忽略了“{}” </span><span> </span></span></li>
<li><span>statement; </span></li>
</ol>

The comment format can also be like the following In this way,

is written as follows:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">if</span><span> (condition) {  </span></span></li>
<li>
<span class="comment">/*进行操作的条件*/</span><span> </span>
</li>
<li class="alt"><span>statements;  </span></li>
<li>
<span>} </span><span class="keyword">else</span><span> {  </span>
</li>
<li class="alt">
<span class="comment">/*进行操作的条件*/</span><span> </span>
</li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

As long as the relationship between the branches can be clearly described, comments can be written anywhere

5 for statements

A for statement should have the following format:

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">for</span><span> (initialization; condition; update) {  </span></span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

An empty for statement (all work (all done in initialization, conditional judgment, update clause) should have the following format:

<ol class="dp-c"><li class="alt"><span><span class="keyword">for</span><span> (initialization; condition; update); </span></span></li></ol>

When using commas in the initialization or update clause of a for statement, avoid using more than three variables, This leads to increased complexity. If necessary, you can use separate statements before the for loop (for the initialization clause) or at the end of the for loop (for the update clause).

6 while statement

A while statement should have the following format

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">while</span><span> (condition) {  </span></span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

a An empty while statement should have the following format:

<ol class="dp-c"><li class="alt"><span><span class="keyword">while</span><span> (condition); </span></span></li></ol>

7 do...while statement

A do-while statement should have the following format:

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">do</span><span> {  </span></span></li>
<li><span>statements;  </span></li>
<li class="alt">
<span>} </span><span class="keyword">while</span><span> (condition); </span>
</li>
</ol>

8 switch statement

A switch statement should have the following format:

The following is the quote Content:

<ol class="dp-c">
<li class="alt"><span><span class="keyword">switch</span><span> (condition) {  </span></span></li>
<li>
<span></span><span class="keyword">case</span><span> ABC:   </span>
</li>
<li class="alt">
<span></span><span class="comment">/* falls through */</span><span> </span>
</li>
<li><span>statements;  </span></li>
<li class="alt">
<span></span><span class="keyword">case</span><span> DEF:  </span>
</li>
<li><span>　statements;  </span></li>
<li class="alt">
<span>　</span><span class="keyword">break</span><span>;  </span>
</li>
<li>
<span></span><span class="keyword">case</span><span> XYZ:  </span>
</li>
<li class="alt"><span>statements;  </span></li>
<li>
<span></span><span class="keyword">break</span><span>;  </span>
</li>
<li class="alt">
<span></span><span class="keyword">default</span><span>:  </span>
</li>
<li><span>statements;  </span></li>
<li class="alt">
<span></span><span class="keyword">break</span><span>;  </span>
</li>
<li><span>} </span></li>
</ol>

Whenever a case is executed downwards (because there is no break statement), comments should usually be added at the location of the break statement. The above example code contains the comment /* falls through */.

9 try...catch statement

A try-catch statement should have the following format:

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span>try {  </span></span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} catch (ExceptionClass e) {  </span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

A try-catch statement may also be followed by a finally statement, which will be executed regardless of whether the try code block is successfully executed.

The following is the quoted content:

<ol class="dp-c">
<li class="alt"><span><span>try {  </span></span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} catch (ExceptionClass e) {  </span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} finally {  </span></li>
<li><span>statements;  </span></li>
<li class="alt"><span>} </span></li>
</ol>

I hope that the introduction of this article can be helpful to you.

http://www.bkjia.com/PHPjc/445733.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/445733.htmlTechArticleThe following introduces the programming statements in the PHP programming language. 1 A simple statement contains at most one statement per line, for example: The following is the quoted content: $argv ++; //Correct $argc --; //Correct...