How does escaping work in PHP strings and why does the number of backslashes change when outputting or processing the string?

When working with PHP strings, escaping is used to include special characters like quotes or backslashes within the string. The number of backslashes needed can change when outputting or processing the string because of how PHP interprets escape sequences. To ensure the correct number of backslashes is used, you can use the `addslashes()` function to escape special characters in a string before outputting it.

$string = 'This is a "quoted" string';
$escaped_string = addslashes($string);
echo $escaped_string;