What are the differences between using echo and include when integrating PHP files in a script?

When integrating PHP files in a script, using "include" will include and evaluate the specified file, allowing the script to continue even if the file is not found. On the other hand, using "echo" will simply output the contents of the file as a string, without evaluating any PHP code within it. Therefore, if you want to include and run PHP code from another file within your script, you should use "include".

// Using include to integrate PHP files in a script
include 'file.php';