Removes duplicate values from an array

Description

array_unique ( array $array [, int $sort_flags = SORT_STRING ] ) : array

Takes an input array and returns a new array without duplicate values.

Note that keys are preserved. If multiple elements compare equal under the given sort_flags, then the key and value of the first equal element will be retained.

Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2 i.e. when the string representation is the same, the first element will be used.

Parameters

array

The input array.

sort_flags

The optional second parameter sort_flags may be used to modify the sorting behavior using these values:

Sorting type flags:

SORT_REGULAR - compare items normally (don't change types)
SORT_NUMERIC - compare items numerically
SORT_STRING - compare items as strings
SORT_LOCALE_STRING - compare items as strings, based on the current locale.

Return Values

Returns the filtered array.

Changelog

Version	Description
7.2.0	If `sort_flags` is `SORT_STRING`, formerly `array` has been copied and non-unique elements have been removed (without packing the array afterwards), but now a new array is built by adding the unique elements. This can result in different numeric indexes.
5.2.10	Changed the default value of `sort_flags` back to `SORT_STRING`.
5.2.9	Added the optional `sort_flags` defaulting to `SORT_REGULAR`. Prior to 5.2.9, this function used to sort the array with `SORT_STRING` internally.

Examples

Example #1 array_unique() example


<?php
$input = array("a" => "green", "red", "b" => "green", "blue", "red");
$result = array_unique($input);
print_r($result);
?>

The above example will output:

Array
(
    [a] => green
    [0] => red
    [1] => blue
)

Example #2 array_unique() and types


<?php
$input = array(4, "4", "3", 4, 3, "3");
$result = array_unique($input);
var_dump($result);
?>

The above example will output:

array(2) {
  [0] => int(4)
  [2] => string(1) "3"
}

Notes

Note: Note that array_unique() is not intended to work on multi dimensional arrays.

array_unique