How can the use of single quotes versus double quotes impact the output of PHP code, especially when dealing with HTML attributes?

When dealing with HTML attributes in PHP code, using single quotes versus double quotes can impact the output. Double quotes allow for variable interpolation, meaning PHP variables within the string will be evaluated and replaced with their values. Single quotes treat everything within them as a literal string, so variables will not be evaluated. To ensure proper output of HTML attributes with PHP variables, use double quotes around the attribute values.

<?php
$name = "John Doe";
echo "<input type='text' value='$name'>";
?>