PHP array_unique() Function

The PHP array_unique() function removes duplicate values from an array, preserving the first occurrence of each value and reindexing the array with keys preserved. It's useful for filtering out redundant data and ensuring a collection of unique elements within an array.

Syntax

array array_unique($array , $sort_flags)

Note: The keys of the array are preserved. That is, the keys of the not-removed elements of the input array will be the same in the output array.

Parameters

: This function accepts two parameters out of which one is mandatory and the other is optional. Both of these parameters are described below:

1. $array: This parameter is mandatory to be supplied and it specifies the input array from which we want to remove duplicates.
2. $sort_flags: This is optional parameter. This parameter $sort_flags may be used to modify the sorting behavior using these values:
   • SORT_REGULAR: This is the default value of the parameter $sort_flags. This value tells the function to compare items normally (don't change types).
   • SORT_NUMERIC: This value tells the function to compare items numerically.
   • SORT_STRING: This value tells the function to compare items as strings.
   • SORT_LOCALE_STRING: This value tells the function to compare items as strings, based on the current locale.

Return Value: The array_unique() function returns the filtered array after removing all duplicates from the array.

Below programs illustrate the array_unique() function in PHP:

Example : In this example we removes duplicate values from the array a using array_unique() and prints the result.

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

Example 2: In this example we removes duplicate values from the associative array arr using array_unique() and prints the result.

Array
(
 [a] => MH
 [b] => JK
 [d] => OR
)