Check if all elements in Array are unique in PHP

This tutorial will discuss about unique ways to check if all elements in array are unique in php.

Table Of Contents

Method 1: Using array_unique() function

The array_unique()function in PHP, accepts an array as an argument, and returns a new array without duplicate values.

So, to check if an array $arr contains only unique elements, pass that array $arr to the array_unique()function. It will return a new array $uniqArr, then compare the size of this new array and the size of original array i.e. $arr. If the size is equal, then it means both the arrays are equal.

Let’s see the complete example,

<?php
$arr = [11, 42, 33, 56, 78, 29];

// Get an array of unique elements
$uniqArr = array_unique($arr);

// Check if the count of elements in array
// and unique array is equal
if (count($uniqArr) === count($arr)) {
  echo "Yes, all elements of array are unique";
} else {
  echo "No, all elements of array are not unique";
}
?>

Output

Yes, all elements of array are unique

Method 2: Using foreach() and in_array()

Intialize an new array $uniqArr, it will store unique elements only. Then iterate over all the elements of original array $arr, and for each element check it exists in the new array $uniqArr or not. If exists, then mark the result as false and break the loop. If it does not exists in the unique array $uniqArr, then add it.

At the end of loop if the result is true, then it means array has duplicate values.

Let’s see the complete example,

<?php
$arr = [11, 42, 33, 56, 78, 29];

// A new array to store unique elements only
$uniqArr = [];

$result = true;

// Iterate over all elements of array
foreach ($arr as $element) {
  // Check if exist in another array
  if (in_array($element, $uniqArr)) {
    $result = false;
    break;
  }
  $uniqArr[] = $element;
}

if ($result) {
  echo "Yes, all elements of array are unique";
} else {
  echo "No, all elements of array are not unique";
}
?>

Output

Yes, all elements of array are unique

Summary

We learned about two ways to check if an array has unique values only in PHP.