how to add a variable to a string php code example

Example 1: php concat

$a = "hello";
$b = "world";
$c = $a . " " . $b;

echo $c; // hello world

Example 2: how to combine variables and text into a string php

<?php
$number = 8;
$txt = "the number is".$number.", ok?"; //Use a dot to combine
echo $txt;
?>