how to add variable inside string php code example

Example 1: 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;
?>

Example 2: php concat variable and string

<?php
  $name = "Paul";	
  $age = 26;

  echo "My name is {$name}, I'm {$age} years old ";