PHP foreach循环

foreach()有两种用法：

1： 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。

2：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”.

 

 

示范用法的更多例子：

<?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 />';

}

 

/*-------------------------------------------------------------------------*/

/* 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++;

}

 

/*-------------------------------------------------------------------------*/

/* 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 />';

}

 

/*-------------------------------------------------------------------------*/

/* 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 ";

    }

}

 

/*-------------------------------------------------------------------------*/

/* 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 ";

}

?>

 

结果如下:

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) 
$a[0] => 1
$a[1] => 2
$a[2] => 3
$a[3] => 17


foreach example 3: key and value 
$a[one] => 1
$a[two] => 2
$a[three] => 3
$a[seventeen] => 17


foreach example 4: multi-dimensional arrays 
a b y z 

foreach example 5: dynamic arrays 
1 2 3 4 5

 

感谢：http://apps.hi.baidu.com/share/detail/793606