Problem in function replacing strings in multidimensional array

Question

I've created this function to replace strings in multidimensional arrays.

function replace_in_array($find, $replace, & $array) {

  array_walk_recursive($array, function( & $array) use($find, $replace) {    
    if ($array == $find) {
      $array = $replace;
    }
  });

  return $array;
}

For the most part it works. But sometimes it replaces the string where it's not supposed too.

While I run it like this replace_in_array('hello', 'hey', $array) things like this get replaced.

'age' => true, or 'age' => 0

My array has about 300 keys and values. For the most part it works. Just a few get replaced when not supposed too. Any idea what im doing wrong here? Thanks