magic_quotes_gpc, magic_quotes_runtime

Magic quotes is the name of a PHP feature that automatically quotes input
data, by using the addslashes() function. Historically, this was used so that
form data could be used directly in SQL queries without any security or quoting
issues. Today, form data is used for much more, and magic quotes quickly
get in the way. We recommend that you disable this feature, but portable code
must be aware of these settings and deal with them appropriately by calling
stripslashes() on GPS (GET, POST, and cookie) data.