Remove Duplicate Elements from an Array in PHP

In this tutorial, we will introduce the way to remove duplicate elements from a php array using php array_flip() function.

PHP array_flip() function can exchange the key and value of a php array. In order to use it to remove elements from an array, we can do as follows:

1. Create an array which contains some duplicate elements

<?php
$a = array(1, 5, 2, 5, 1, 3, 2, 4, 5);
print_r($a);
?>

The php array $a is:

Array
(
    [0] => 1
    [1] => 5
    [2] => 2
    [3] => 5
    [4] => 1
    [5] => 3
    [6] => 2
    [7] => 4
    [8] => 5
)

2. Flip php array key and value using array_filp()

<?php
$a = array_flip($a); 
print_r($a);
?>

Then $a will be:

Array
(
    [1] => 4
    [5] => 8
    [2] => 6
    [3] => 5
    [4] => 7
)

3. Use array_flip() again

<?php
$a = array_flip($a); 
print_r($a);
?>

The array $a is:

Array
(
    [4] => 1
    [8] => 5
    [6] => 2
    [5] => 3
    [7] => 4
)

4. Re-order the array keys

<?php
$a= array_values($a); 
print_r($a);
?>

Finally, $a is:

Array
(
    [0] => 1
    [1] => 5
    [2] => 2
    [3] => 3
    [4] => 4
)

It does not contain any duplicate elements.

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