How to replace a piece of a string with another piece?

Question

PHP

Actually the problem is to replace the city identifier (number) in api vk with a normal name.
There is a line like:
"name": Vasya
"birthday": 1/1/1990
"city": 1
And a line like this:
"name": Moscow
So, I need to swap "1" and "Moscow" and output one normal line, to make it clear what kind of city.

Answer 1

$cities = json_decode($citiesVk, true);
$citiesNamesMap = array_column($cities, 'name', 'id');

$user = json_decode($vkUser, true);
$user['city'] = $citiesNamesMap($user['city']);

somehow so visible. And here the lines ...
But if you specifically answer your question - regular expressions will cope with this. Specifically preg_replace_callback