Finding the Position of an Element in an Array (PHP Cookbook)

4.13. Finding the Position of an Element in an Array

4.13.1. Problem

You want know if an element is in an array, and, if it is, you want to know where it is located.

4.13.2. Solution

Use array_search( ). It returns the key of the found element or false:

$position = array_search($array, $value);
if ($position !== false) {
    // the element in position $position has $value as its value in array $array
}

4.13.3. Discussion

Use in_array( ) to find if an array contains a value; use array_search( ) to discover where that value is located. However, because array_search( ) gracefully handles searches in which the value isn't found, it's better to use array_search( ) instead of in_array( ). The speed difference is minute, and the extra information is potentially useful:

$favorite_foods = array(1 => 'artichokes', 'bread', 'cauliflower', 'deviled eggs');
$food = 'cauliflower';
$position = array_search($food, $favorite_foods);

if ($position !== false) {
    echo "My #$position favorite food is $food";
} else {
    echo "Blech! I hate $food!";
}

Use the !== check against false because if your string is found in the array at position 0, the if evaluates to a logical false, which isn't what is meant or wanted.

If a value is in the array multiple times, array_search() is only guaranteed to return one of the instances, not the first instance.

4.13.4. See Also

Recipe 4.12 for checking whether an element is in an array; documentation on array_search( ) at http://www.php.net/array-search; for more sophisticated searching of arrays using regular expression, see preg_replace( ) at http://www.php.net/preg-replace and Chapter 13.