PHP sends the values ​​in the array to the user-defined function and returns a string function array_reduce()

Example

Send the values ​​in the array to the userCustom function, and return a string:

<?php
function myfunction($v1,$v2)
{
return $v1 . "-" . $v2;
}
$a=array("Dog","Cat","Horse");
print_r(array_reduce($a,"myfunction"));
?>

Definition and usage

array_reduce () function sends the values ​​in the array to the user-defined function and returns a string.

Note: If the array is empty or the initial value is not passed, this function returns NULL.

Syntax

array_reduce(array,myfunction,initial)

Parameters	Description
array	Required. Specifies an array.
myfunction	Required. Specifies the name of the function.
initial	Optional. Specifies the first value sent to the function for processing.

Technical details

Return value:	Return the result value.
PHP Version:	4.0.5+
Change Log:	Since PHP 5.3.0, the initial parameter accepts multiple types (mixed), and versions before PHP 5.3.0 only support integers.

更多实例

实例 1

带 initial 参数：

<?php
function myfunction($v1,$v2)
{
return $v1 . "-" . $v2;
}
$a=array("Dog","Cat","Horse");
print_r(array_reduce($a,"myfunction",5));
?>

实例 2

返回总和：

<?php
function myfunction($v1,$v2)
{
return $v1+$v2;
}
$a=array(10,15,20);
print_r(array_reduce($a,"myfunction",5));
?>

array_reduce的强大不仅如此。看下面的例子。将数组$arr的首个元素弹出，作为初始值，避免min($result['min'], $item['min'])中$result为空。

否则最终结果min是空的。

$arr = array( 
    array('min' => 1.5456, 'max' => 2.28548, 'volume' => 23.152), 
    array('min' => 1.5457, 'max' => 2.28549, 'volume' => 23.152), 
    array('min' => 1.5458, 'max' => 2.28550, 'volume' => 23.152), 
    array('min' => 1.5459, 'max' => 2.28551, 'volume' => 23.152), 
    array('min' => 1.5460, 'max' => 2.28552, 'volume' => 23.152), 
); 

$initial = array_shift($arr); 

$t = array_reduce($arr, function($result, $item) { 
    $result['min'] = min($result['min'], $item['min']); 
    $result['max'] = max($result['max'], $item['max']); 
    $result['volume'] += $item['volume']; 

    return $result; 
}, $initial);

 总之，这种写法比foreach更优雅，更少的定义变量。推荐使用。

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