array_unique()

Published Aug 26, 2023
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The array_unique() function returns a new array with any duplicate values removed.

Syntax

array_unique($array, $sort_flags = SORT_STRING)
  • $array: The array from which the duplicate values will be removed.
  • $sort_flags (optional): Specifies how the array will be sorted. By default, it is set to SORT_STRING.

Types of sort flags:

  • SORT_REGULAR: Does not change the types of the items when comparing.
  • SORT_NUMERIC: Treats all items as numbers.
  • SORT_STRING: Treats all items as strings (e.g. “1” and 1 are considered equal).
  • SORT_LOCALE_STRING: Compare items as strings, based on the current locale.

Note: When multiple values are considered equal, only the first key will be retained.

Example

Consider the following $vegetables array:

<?php
$vegetables = array("carrot", "tomato", "potato", "tomato", "cucumber", "potato");
?>

To remove the duplicate values from the array, the array_unique() function can be implemented as below:

<?php
$uniqueVegetables = array_unique($vegetables);
print_r($uniqueVegetables);
?>

The code results in the following output. Note only the first occurrence of tomato and potato are retained.

Array
(
[0] => carrot
[1] => tomato
[2] => potato
[4] => cucumber
)

Codebyte Example

In the code below, the array_unique() function is used to remove duplicate values from the $shoppingList array.

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