How can PHP developers ensure that the HTML code output is readable and well-formatted?

PHP developers can ensure that the HTML code output is readable and well-formatted by using proper indentation and line breaks. This can be achieved by structuring the HTML code in a logical and organized manner within the PHP file. Additionally, developers can utilize PHP's built-in functions like `echo` or `print` to output HTML code, making it easier to maintain and modify the code in the future.

<?php
// Example of well-formatted HTML output using PHP
echo "<html>\n";
echo "<head>\n";
echo "<title>Sample Page</title>\n";
echo "</head>\n";
echo "<body>\n";
echo "<h1>Hello, World!</h1>\n";
echo "<p>This is a sample paragraph.</p>\n";
echo "</body>\n";
echo "</html>\n";
?>