How to replace the value of certain key in array using PHP?

Today I needed to replace the value of certain key in array. I do not need to add another key and value. Rather, replace an existing key's value with another value.
Since I am using an associative array and knew the key's name as well. I wrote the following code and it worked.
PHP

$array = array('product' =>'iphone', 'price' =>'4500', 'model'=>'5G');

$array['price'] = '5700'; // say you wanted to change the value of key 'price'

print_r($array);

//outputs : array('product' =>'iphone', 'price' =>'5700', 'model'=>'5G');

If you could want to rebuild the array and keep the element's order, you can use following function.

<?php
function replace_key($find, $replace, $array) {
 $arr = array();
 foreach ($array as $key => $value) {
  if ($key == $find) {
   $arr[$replace] = $value;
  } else {
   $arr[$key] = $value;
  }
 }
 return $arr;
}

//example
$array = array('test' => 0, 'replace this' => 1, 3 => 'hey');
echo '<pre>', print_r($array, true), '</pre>';
$array = replace_key('replace this', 'with this', $array);
echo '<pre>', print_r($array, true), '</pre>';
?>