Forgot Password ??

PHP , ASP , ASP.NET, VB.NET, C#, Java , jQuery , Android , iOS , Windows Phone

	Registered : 109,037

HOME > PHP Manual > usort - Sort an array by values using a user-defined comparison function

ลองใช้ค้นหาข้อมูล

usort

(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.

Note: If two members compare as equal, their order in the sorted array is undefined.

Note: This function assigns new keys to the elements in array . It will remove any existing keys that may have been assigned, rather than just reordering the keys.

Parameters

array: The input array.
cmp_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.

Return Values

Returns TRUE on success or FALSE on failure.

ChangeLog

Version Description

4.1.0 A new sort algorithm was introduced. The cmp_function doesn't keep the original order for elements comparing as equal.

Examples

Example #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");

foreach ($a as $key => $value) {
    echo "$key: $value\n";
}
?>

The above example will output:

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

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

Example #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.

The above example will output:

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

Example #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: */
    static 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";
}
?>

The above example will output:

b
c
d

	สอน Google Maps Api
	สอน Windows Service
	สอน Entity Framework
	สอน Android
	สอน Java เขียน Java
	Java GUI Swing
	สอน JSP (Web App)
	iOS (iPhone,iPad)
	Windows Phone
	Windows Azure
	Windows Store
	Laravel Framework
	Yii PHP Framework
	สอน jQuery
	สอน jQuery กับ Ajax
	สอน PHP OOP (Vdo)
	Ajax Tutorials
	SQL Tutorials
	สอน SQL (Part 2)
	JavaScript Tutorial
	Javascript Tips
	VBScript Tutorial
	VBScript Validation
	Microsoft Access
	MySQL Tutorials
	-- Stored Procedure
	MariaDB Database
	SQL Server Tutorial
	SQL Server 2005
	SQL Server 2008
	SQL Server 2012
	-- Stored Procedure
	Oracle Database
	-- Stored Procedure
	SVN (Subversion)
	แนวทางการทำ SEO
	ปรับแต่งเว็บให้โหลดเร็ว