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Array Functions
PHP Manual

# array_unique

(PHP 4 >= 4.0.1, PHP 5)

array_unique — Removes duplicate values from an array

### Description

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

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

Note that keys are preserved. array_unique() sorts the values treated as string at first, then will keep the first key encountered for every value, and ignore all following keys. It does not mean that the key of the first related value from the unsorted `array` will be kept.

> Note: Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: 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
--- | ---
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"
    }

### See Also

- array_count_values() - Counts all the values of an array

### Notes

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

array_uintersect
array_unshift
Array Functions
PHP Manual