Руководство по PHP
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usort

(PHP 3>= 3.0.3, PHP 4 , PHP 5)

usort --  Sort an array by values using a user-defined comparison function

Description

bool usort ( array array, callback cmp_function)

This function will sort an array by its values using a user-supplied comparison function. If the array you wish to sort needs to be sorted by some non-trivial criteria, you should use this function.

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

Замечание: If two members compare as equal, their order in the sorted array is undefined. Up to PHP 4.0.6 the user defined functions would keep the original order for those elements, but with the new sort algorithm introduced with 4.1.0 this is no longer the case as there is no solution to do so in an efficient way.

Возвращает TRUE в случае успешного завершения, FALSE в случае возникновения ошибки.

Пример 1. usort() example

<?php
function cmp($a, $b)
{
    if ($a == $b) {
        return 0;
    }
    return ($a < $b) ? -1 : 1;
}

$a = array(3, 2, 5, 6, 1);

usort($a, "cmp");

while (list($key, $value) = each($a)) {
    echo "$key: $value\n";
}
?>

This example would display: 

0: 1
1: 2
2: 3
3: 5
4: 6

Замечание: Obviously in this trivial case the sort() function would be more appropriate.

Пример 2. usort() example using multi-dimensional array

<?php
function cmp($a, $b)
{
    return strcmp($a["fruit"], $b["fruit"]);
}

$fruits[0]["fruit"] = "lemons";
$fruits[1]["fruit"] = "apples";
$fruits[2]["fruit"] = "grapes";

usort($fruits, "cmp");

while (list($key, $value) = each($fruits)) {
    echo "\$fruits[$key]: " . $value["fruit"] . "\n";
}
?>

When sorting a multi-dimensional array, $a and $b contain references to the first index of the array.

This example would display: 

$fruits[0]: apples
$fruits[1]: grapes
$fruits[2]: lemons

Пример 3. usort() example using a member function of an object

<?php
class TestObj {
    var $name;

    function TestObj($name)
    {
        $this->name = $name;
    }

    /* This is the static comparing function: */
    function cmp_obj($a, $b)
    {
        $al = strtolower($a->name);
        $bl = strtolower($b->name);
        if ($al == $bl) {
            return 0;
        }
        return ($al > $bl) ? +1 : -1;
    }
}

$a[] = new TestObj("c");
$a[] = new TestObj("b");
$a[] = new TestObj("d");

usort($a, array("TestObj", "cmp_obj"));

foreach ($a as $item) {
    echo $item->name . "\n";
}
?>

This example would display: 

b
c
d

See also uasort(), uksort(), sort(), asort(), arsort(),ksort(), natsort(), and rsort().

Пред.НачалоСлед.
uksortУровень вышеAspell functions [deprecated]

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