Null Colese Operator

<?php

$default_lat = 23.9;
$default_lon = 90.8;

$user_lat = 20.8;

// output by the ternary operator

//$lat = isset($user_lat) ? $user_lat : $default_lat;

// output by null Coalescing operator

$lat = $user_lat ?? $default_lat;

echo $lat;