第五章_PHP流程控制

　　1.顺序结构

　　2.分支结构

　　　　2.1 if...else

<span 1</span> <?<span php
</span><span 2</span>     <span $today</span>=<span date</span>("w");   <span //</span><span 获取今天星期几</span>
<span 3</span>     <span if</span>(<span $today</span>==0<span ){
</span><span 4</span>         <span echo</span> 'Sunday!'<span ;
</span><span 5</span>     }<span else</span><span {
</span><span 6</span>         <span echo</span> 'Sorry!'<span ;
</span><span 7</span> <span     }
</span><span 8</span> ?>

　　　　2.2 if...elseif

　　　　2.3 switch

　　3.循环结构

　　　　3.1 while

<span 1</span> <?<span php
</span><span 2</span>     <span $num</span>=1<span ;
</span><span 3</span>     <span while</span>(<span $num</span><=100<span ){
</span><span 4</span>         <span echo</span> <span $num</span>.' '<span ;
</span><span 5</span>         <span $num</span>++<span ;
</span><span 6</span> <span     }
</span><span 7</span> ?>

　　　　3.2 do...while

　　　　与C/C++类似

　　　　3.3 for

<span 1</span> <?<span php
</span><span 2</span>     <span $week</span>=<span array</span>('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'<span );
</span><span 3</span>     <span $size</span>=<span count</span>(<span $week</span><span );
</span><span 4</span>     <span echo</span> '数组大小'.<span $size</span>.'<p>'<span ;
</span><span 5</span>     <span for</span>(<span $i</span>=0;<span $i</span><<span $size</span>;<span $i</span>++<span ){
</span><span 6</span>         <span echo</span> <span $week</span>[<span $i</span>].' '<span ;
</span><span 7</span> <span     }
</span><span 8</span> ?>

　　　　3.4 foreach

　　　　foreach语句专门用来遍历数组的，有两种语法格式：

　　　　　　①foreach(数组名 as 元素名){

　　　　　　　　　　语句块;

　　　　　　　}

　　　　　　②foreach(数组名 as 键名 => 元素名){

　　　　　　　　　　语句块;

　　　　　　　}

前者举例如下：

<span 1</span> <?<span php
</span><span 2</span>     <span $week</span>=<span array</span>('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday'<span );
</span><span 3</span>     <span $size</span>=<span count</span>(<span $week</span><span );
</span><span 4</span>     <span echo</span> '数组大小'.<span $size</span>.'<p>'<span ;
</span><span 5</span>     <span foreach</span>(<span $week</span> <span as</span> <span $value</span><span ){
</span><span 6</span>         <span echo</span> <span $value</span>.' '<span ;
</span><span 7</span> <span     }
</span><span 8</span> ?>

后者举例如下：

<span 1</span> <?<span php
</span><span 2</span>     <span $week</span>=<span array</span>('星期日'=>'Sunday','星期一'=>'Monday','星期二'=>'Tuesday','星期三'=>'Wednesday','星期四'=>'Thursday','星期五'=>'Friday','星期六'=>'Saturday'<span );
</span><span 3</span>     <span $size</span>=<span count</span>(<span $week</span><span );
</span><span 4</span>     <span echo</span> '数组大小'.<span $size</span>.'<p>'<span ;
</span><span 5</span>     <span foreach</span>(<span $week</span> <span as</span> <span $key</span>=><span $value</span><span ){
</span><span 6</span>         <span echo</span> <span $key</span>.':'.<span $value</span>.' '<span ;
</span><span 7</span> <span     }
</span><span 8</span> ?>

　　4.break 与 continue

　　break后面可以接一个数字，表示跳出第几重循环，continue后面也可以接一个数字，表示跳出第几重循环后面尚未执行的语句。