What are the differences between htmlentities and htmlspecialchars in PHP, and when should each be used?

htmlentities and htmlspecialchars are both PHP functions used to convert special characters to their HTML entities, preventing cross-site scripting attacks. The main difference between the two is that htmlentities converts all characters with HTML entities, while htmlspecialchars only converts characters that have special meaning in HTML (such as < and >). htmlentities should be used when you want to convert all characters to HTML entities, while htmlspecialchars should be used when you only want to convert characters that have special meaning in HTML.

// Using htmlentities to convert all characters to HTML entities
$encoded_string = htmlentities($original_string);

// Using htmlspecialchars to convert only characters with special meaning in HTML to HTML entities
$encoded_string = htmlspecialchars($original_string);