check where key in associative array have a value

// Here's our fruity array
$fruits = ['apple', 'pear', 'banana'];

// Use it in an `if` statement
if (array_key_exists("banana", $fruits)) {
 // Do stuff because `banana` exists
}

// Store it for later use
$exists = array_key_exists("peach", $fruits);<?php
$search_array = array('first' => 1, 'second' => 4);
if (array_key_exists('first', $search_array)) {
    echo "The 'first' element is in the array";
}
?>