Provide RegEx feature for array_key_exists function

Hi,

  Here is the function which can take the $key as a RegEx/String. This function checks whether the given string($string) is a Regular Expression or not. If yes, it will use preg_match() function else it will use array_key_exists()  function.

function preg_array_key_exists($filename, $array) {
    $available = false;  
    if (array_key_exists($filename, $array))
    {
        $available = true;      
    }
    else
    {      
        $keys = array_keys($array);
        foreach ($keys as $key) {        
            if (@preg_match($key, $filename) == 1) {  
              $available = true;          
          }      
        }
    }
    return $available;
}