PHP数组函数array_walk()笔记
PHP数组函数array_walk()笔记
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...)
参数 | 描述 |
---|---|
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:&$value。(参见例子 3)
注释:将键名和 userdata 传递到 function 中是 PHP 4.0 新增加的。
例子 1
<?php function myfunction($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 Cat
The key b has the value Dog
The key c has the value Horse
例子 2
带有一个参数:
<?php function 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 Cat
b has the value Dog
c has the value Horse
例子 3
改变数组元素的值(请注意 &$value):(这种情况用的比较多!)
<?php function myfunction(&$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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