How to check a key exist in an array?

PHP array_key_exists() Function is used to check a key exist or not in an array.

Example Uses

<?php
$a=array("fruit"=>"Apple","Car"=>"BMW");
if (array_key_exists("Apple",$a))
  {
  echo "Array Key exists!";
  }
else
  {
  echo "Array Key does not exist!";
  }
?>