How does the backslash alter the function of characters in PHP strings?

The backslash is used in PHP strings as an escape character to alter the function of certain characters. For example, a backslash before a double quote " will escape the quote and allow it to be included in the string without terminating it. Similarly, a backslash before a backslash itself will escape the backslash character. Example: To include a double quote within a string, use the backslash as an escape character:

$string = "This is a \"quoted\" string.";
echo $string; // Output: This is a "quoted" string.