PHP array_walk() 函数
定义和用法
array_walk() 函数对数组中的每个元素应用回调函数。如果成功则返回 TRUE,否则返回 FALSE。
典型情况下 function 接受两个参数。array 参数的值作为第一个,键名作为第二个。如果提供了可选参数 userdata ,将被作为第三个参数传递给回调函数。
如果 function 函数需要的参数比给出的多,则每次 array_walk() 调用 function 时都会产生一个 E_WARNING 级的错误。这些警告可以通过在 array_walk() 调用前加上 PHP 的错误操作符 @ 来抑制,或者用 error_reporting()。
语法array_walk(array,function,userdata...)
array | 必需。规定数组。 |
function | 必需。用户自定义函数的名称。 |
userdata | 可选。用户输入的值,可作为回调函数的参数。 |
提示和注释
提示:您可以为函数设置一个或多个参数。
注释:如果回调函数需要直接作用于数组中的值,可以将回调函数的第一个参数指定为引用:&$value。(参见例子 3)
注释:将键名和 userdata 传递到 function 中是 PHP 4.0 新增加的。
例子 1
<?phpfunction myfunction($value,$key) {echo "The key $key has the value $value<br />";}$a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse");array_walk($a,"myfunction");?>
输出:
The key a has the value CatThe key b has the value DogThe key c has the value Horse
例子 2
带有一个参数:
<?phpfunction myfunction($value,$key,$p) {echo "$key $p $value<br />";}$a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse");array_walk($a,"myfunction","has the value");?>
输出:
a has the value Catb has the value Dogc has the value Horse
例子 3
改变数组元素的值(请注意 &$value):
<?phpfunction myfunction(&$value,$key) {$value="Bird;}$a=array("a"=>"Cat","b"=>"Dog","c"=>"Horse");array_walk($a,"myfunction");print_r($a);?>
输出:
Array ( [a] => Bird [b] => Bird [c] => Bird )

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