php中foreach的两种使用方法介绍

php中用foreach来操作数组的代码

foreach()有两种用法：

foreach(array_name as $value) { statement; }

这里的array_name是你要遍历的数组名，每次循环中，array_name数组的当前元素的值被赋给$value,并且数组内部的下标向下移一 步，也就是下次循环回得到下一个元素。

foreach(array_name as $key => $value) { statement; }

这里跟第一种方法的区别就是多了个$key,也就是除了把当前元素的值赋给$value外，当前元素的键值也会在每次循环中被赋给变量$key。键值可以 是下标值，也可以是字符串。比如book[0]=1中的"0"，book[id]="001"中的"id".
程序实例1：

<?php /*-------------------------------------------------------------------------*/ /* foreach example 1: value only */ echo "foreach example 1: value only ".'<br />'; $a = array(1, 2, 3, 17); foreach ($a as $v) { echo "Current value of ".$a.":". $v."<br />"; } ?>

// 运行结果
foreach example 1: value only
Current value of $a: 1
Current value of $a: 2
Current value of $a: 3
Current value of $a: 17

/*-------------------------------------------------------------------------*/ /* foreach example 2: value (with key printed for illustration) */ echo '<br />'.'<br />'."foreach example 2: value (with key printed for illustration) ".'<br />'; $a = array(1, 2, 3, 17); $i = 0; /* for illustrative purposes only */ foreach ($a as $v) { echo ""$a[$i] => $v".'<br />'; $i++; } // 程序运行结果 foreach example 2: value (with key printed for illustration) $a[0] => 1 $a[1] => 2 $a[2] => 3 $a[3] => 17

/*-------------------------------------------------------------------------*/ /* foreach example 3: key and value */ echo '<br />'.'<br />'."foreach example 3: key and value ".'<br />'; $a = array( "one" => 1, "two" => 2, "three" => 3, "seventeen" => 17 ); foreach ($a as $k => $v) { echo ""$a[$k] => $v".'<br />'; } // 程序运行结果 foreach example 3: key and value $a[one] => 1 $a[two] => 2 $a[three] => 3 $a[seventeen] => 17

/*-------------------------------------------------------------------------*/ /* foreach example 4: multi-dimensional arrays */ echo '<br />'.'<br />'."foreach example 4: multi-dimensional arrays ".'<br />'; $a = array(); $a[0][0] = "a"; $a[0][1] = "b"; $a[1][0] = "y"; $a[1][1] = "z"; foreach ($a as $v1) { foreach ($v1 as $v2) { echo "$v2"n"; } } // 程序运行结果 foreach example 4: multi-dimensional arrays a b y z

/*-------------------------------------------------------------------------*/ /* foreach example 5: dynamic arrays */ echo '<br />'.'<br />'."foreach example 5: dynamic arrays ".'<br />'; foreach (array(1, 2, 3, 4, 5) as $v) { echo "$v"n"; } // 程序运行结果 foreach example 5: dynamic arrays 1 2 3 4 5

也可以这么用：

$messageNav['首页'] =ROOT_PATH; $messageNav[&#39<em style="color:transparent">本文来源[email protected]搞@^&代*@码)网9</em><strong>搞代gaodaima码</strong>;人才交流'] ="#" $messageNav['动态专栏'] ="hragent/cn/" <?php $i = 0;foreach ($messageNav as $key=>$value):?> <?php if ($i != count($messageNav) - 1):?> <a href="<?=$value?>"><?=$key?></a>> <?php else:?> <a href="<?=$value?>" class="onlink"><?=$key?></a> <?php endif;?> <?php $i++;endforeach;?>

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