Mastering PHP’s in_array(): How to Check Values in Arrays Efficiently

Function Overview

The in_array() function checks whether a given value ( $needle) exists in an array ( $haystack). If the optional $strict flag is omitted, the function performs a loose comparison; when $strict is TRUE, both value and type must match.

Parameters

needle : The value to search for. If it is a string, the comparison is case‑sensitive.

haystack : The array to be searched.

strict : Optional boolean. When TRUE, in_array() also checks that the type of needle matches the type of the corresponding element in haystack.

Return Value

Returns TRUE if needle is found in haystack; otherwise returns FALSE.

Example

<?php
$os = array("Mac", "NT", "Irix", "Linux");
if (in_array("Irix", $os)) {
    echo "Got Irix";
}
if (in_array("mac", $os)) {
    echo "Got mac";
}
?>

Output

Got Irix