PHP array_unique()

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");
?>

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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);
?>

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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
)

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Codebyte Example

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

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