PHP 8 reference · Array Functions

PHP array_unique() Function

Remove duplicate values from an array, keeping the first occurrence of each and its key.

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Syntax

array_unique(array $array, int $flags = SORT_STRING): array

Parameter	Description
`array`	The input array.
`flags` optional	How values are compared: `SORT_STRING`, `SORT_REGULAR`, `SORT_NUMERIC`. Default: `SORT_STRING`

The array without duplicates (original keys kept).

Remove duplicatesTry it yourself

<?php
print_r(array_unique(["php", "sql", "php", "css", "sql"]));

Output

Array
(
    [0] => php
    [1] => sql
    [3] => css
)

Ignore case and renumberTry it yourself

<?php
$tags = ["PHP", "php", "Php"];
print_r(array_values(array_unique(array_map("strtolower", $tags))));

Output

Array
(
    [0] => php
)

Version	Change
PHP 4.0	Added

array_count_values() · Count how many times each value occurs in an array, returning value => count pairs.
array_flip() · Swap keys and values, so each value becomes a key. Values must be strings or integers; duplicates keep the last key.
array_values() · Return all the values of an array as a list re-indexed from 0. Often used after array_filter() or unset().
PHP Arrays · tutorial
PHP Array Functions · tutorial