PHP - usort

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Metóda - usort

(PHP 4, PHP 5, PHP 7)

The function is used to sort an array by values using a comparison function defined by the user.

Note: Any existing keys will be removed and new keys will be assigned.

Procedurálne

• function usort (array &$array, callable $value_compare_func) : bool
• function callback () : array

Parametre

Názov	Dátový typ	Predvolená hodnota	Popis
&$array	array		The array we want to sort.
$value_compare_func	callable		Specifies a callable comparison function. The function must return a negative integer if the first argument of the function is less than the second argument, a positive integer if it's greater or zero if they're equal.

Mávratovej hodnoty

Vracia: bool

Returns true on success, returns false otherwise .

Príklady

In the first example we sort names according to their lengths:

<?php
$names = array("Elizabeth", "Lisa", "Karen", "Jennifer", "Dorothy", "Sandra");
// The function compares the length of the names:
function compare_name_length($name1, $name2) {
    if(strlen($name1) == strlen($name2)) {
        return 0;
    } else {
        return (strlen($name1) < strlen($name2)) ? -1 : 1;
    }
}
// Sorting the array according to our comparison function:
usort($names, "compare_name_length");

foreach ($names as $name) {
    echo $name . "<br>";
}

In the second example we sort users (an associative array) according to their last name.

<?php
// An associative array we want to sort:
$users = array(
    array("firstName" => "John", "lastName" => "Rambo", "age" => 30),
    array("firstName" => "Chuck", "lastName" => "Norris", "age" => 40),
    array("firstName" => "John", "lastName" => "McClane", "age" => 35),
    array("firstName" => "Rocky", "lastName" => "Balboa", "age" => 25),
    array("firstName" => "James", "lastName" => "Bond", "age" => 35),
);
// Our function using the built-in strnatcmp() comparison function
function compare_lastName($user1, $user2) {
    return strnatcmp($user1["lastName"], $user2["lastName"]);
}
// Sorting the array according to our comparison function:
usort($users, "compare_lastName");

foreach ($users as $user) {
    print_r($user);
    echo "<br>";
}