What is the significance of using single quotes instead of double quotes in PHP code within JavaScript strings?

Using single quotes instead of double quotes in PHP code within JavaScript strings is significant because it prevents conflicts with double quotes used in the JavaScript code. When PHP code is embedded within JavaScript strings using double quotes, it can lead to syntax errors or unexpected behavior. By using single quotes for PHP code within JavaScript strings, you can avoid these issues and ensure proper execution of the code.

<?php
$variable = 'Hello, world!';
echo "<script> var message = '{$variable}'; </script>";
?>