change double quotes to single quotes php in variable code example

Example 1: php quotations within quotations

<?php
  echo '<span onclick="$(this).addClass(\'selected\');"> </span>';
?>

Example 2: how to put php code in single quotes

how to put php code in single quotes

Example 3: how to print any string in double quotes in php

$web = "...if (url.contains(\".mp4\"))..."