PHP array_reduce function

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array_reduce

(PHP 4 >= 4.0.5, PHP 5)

array_reduce() applies iteratively the
function function to the elements of the
array input, so as to reduce the array to
a single value. If the optional initial is
available, it will be used at the beginning of the process, or as
a final result in case the array is empty.
If the array is empty and initial is not passed,
array_reduce() returns NULL.

Example 1. array_reduce() example

function rsum($v, $w)
{
    $v += $w;
    return $v;
}
 
function rmul($v, $w)
{
    $v *= $w;
    return $v;
}
 
$a = array(1, 2, 3, 4, 5);
$x = array();
$b = array_reduce($a, "rsum");
$c = array_reduce($a, "rmul", 10);
$d = array_reduce($x, "rsum", 1);

This will result in $b containing
15, $c containing
1200 (= 10*1*2*3*4*5), and
$d containing 1.

See also array_filter(),
array_map(),
array_unique(), and
array_count_values().