Magic Quotes



This feature has been DEPRECATED and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

Magic Quotes is a process that automagically escapes incoming data to the PHP script. It's preferred to code with magic quotes off and to instead escape the data at runtime, as needed.

What are Magic Quotes

When on, all ' (single-quote), " (double quote), \ (backslash) and NULL characters are escaped with a backslash automatically. This is identical to what addslashes() does.

There are three magic quote directives:

  • magic_quotes_gpc Affects HTTP Request data (GET, POST, and COOKIE). Cannot be set at runtime, and defaults to on in PHP. See also get_magic_quotes_gpc().
  • magic_quotes_runtime If enabled, most functions that return data from an external source, including databases and text files, will have quotes escaped with a backslash. Can be set at runtime, and defaults to off in PHP. See also set_magic_quotes_runtime() and get_magic_quotes_runtime().
  • magic_quotes_sybase If enabled, a single-quote is escaped with a single-quote instead of a backslash. If on, it completely overrides magic_quotes_gpc. Having both directives enabled means only single quotes are escaped as ''. Double quotes, backslashes and NULL's will remain untouched and unescaped. See also ini_get() for retrieving its value.


The very reason magic quotes are deprecated is that a one-size-fits-all approach to escaping/quoting is wrongheaded and downright dangerous.  Different types of content have different special chars and different ways of escaping them, and what works in one tends to have side effects elsewhere.  Any sample code, here or anywhere else, that pretends to work like magic quotes --or does a similar conversion for HTML, SQL, or anything else for that matter -- is similarly wrongheaded and similarly dangerous.

Magic quotes are not for security.  They never have been.  It's a convenience thing -- they exist so a PHP noob can fumble along and eventually write some mysql queries that kinda work, without having to learn about escaping/quoting data properly.  They prevent a few accidental syntax errors, as is their job.  But they won't stop a malicious and semi-knowledgeable attacker from trashing the PHP noob's database.  And that poor noob may never even know how or why his database is now gone, because magic quotes (or his spiffy "i'm gonna escape everything" function) gave him a false sense of security.  He never had to learn how to really handle untrusted input.

Data should be escaped where you need it escaped, and for the domain in which it will be used.  (mysql_real_escape_string -- NOT addslashes! -- for MySQL (and that's only unless you have a clue and use prepared statements), htmlentities or htmlspecialchars for HTML, etc.)  Anything else is doomed to failure.
2011-03-14 10:38:54

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