The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead

Question

When I attempt to connect to a MySQL server from PHP, I see the following error:

Deprecated: The mysql extension is deprecated and will be removed in the future: use mysqli or PDO instead in /path/to/filename.php on line 123

The code on the referenced line is:

mysql_connect($server, $username, $password);

I am certain that the arguments are correct, and this exact code has been working for years without problem. Indeed, I obtained it from a well-sourced tutorial on PHP.

1. Why is this happening?

2. How can I fix it?

3. I understand that it's possible to suppress deprecation errors by setting error_reporting in php.ini to exclude E_DEPRECATED:

   error_reporting = E_ALL ^ E_DEPRECATED
   

   What will happen if I do that?

Answer 1

1. Why is this happening?

   The entire ext/mysql PHP extension, which provides all functions named with the prefix mysql_, was officially deprecated in PHP v5.5.0 and removed in PHP v7.

   It was originally introduced in PHP v2.0 (November 1997) for MySQL v3.20, and no new features have been added since 2006. Coupled with the lack of new features are difficulties in maintaining such old code amidst complex security vulnerabilities.

   The manual has contained warnings against its use in new code since June 2011.

2. How can I fix it?

   As the error message suggests, there are two other MySQL extensions that you can consider: MySQLi and PDO_MySQL, either of which can be used instead of ext/mysql. Both have been in PHP core since v5.0, so if you're using a version that is throwing these deprecation errors then you can almost certainly just start using them right away—i.e. without any installation effort.

   They differ slightly, but offer a number of advantages over the old extension including API support for transactions, stored procedures and prepared statements (thereby providing the best way to defeat SQL injection attacks). PHP developer Ulf Wendel has written a thorough comparison of the features.

   Hashphp.org has an excellent tutorial on migrating from ext/mysql to PDO.

3. I understand that it's possible to suppress deprecation errors by setting error_reporting in php.ini to exclude E_DEPRECATED:

   error_reporting = E_ALL ^ E_DEPRECATED
   

   What will happen if I do that?

   Yes, it is possible to suppress such error messages and continue using the old ext/mysql extension for the time being. But you really shouldn't do this—this is a final warning from the developers that the extension may not be bundled with future versions of PHP (indeed, as already mentioned, it has been removed from PHP v7). Instead, you should take this opportunity to migrate your application now, before it's too late.

   Note also that this technique will suppress all E_DEPRECATED messages, not just those to do with the ext/mysql extension: therefore you may be unaware of other upcoming changes to PHP that would affect your application code. It is, of course, possible to only suppress errors that arise on the expression at issue by using PHP's error control operator—i.e. prepending the relevant line with @—however this will suppress all errors raised by that expression, not just E_DEPRECATED ones.

---

What should you do?

• You are starting a new project.

  There is absolutely no reason to use ext/mysql—choose one of the other, more modern, extensions instead and reap the rewards of the benefits they offer.

• You have (your own) legacy codebase that currently depends upon ext/mysql.

  It would be wise to perform regression testing: you really shouldn't be changing anything (especially upgrading PHP) until you have identified all of the potential areas of impact, planned around each of them and then thoroughly tested your solution in a staging environment.

  • Following good coding practice, your application was developed in a loosely integrated/modular fashion and the database access methods are all self-contained in one place that can easily be swapped out for one of the new extensions.

    Spend half an hour rewriting this module to use one of the other, more modern, extensions; test thoroughly. You can later introduce further refinements to reap the rewards of the benefits they offer.

  • The database access methods are scattered all over the place and cannot easily be swapped out for one of the new extensions.

    Consider whether you really need to upgrade to PHP v5.5 at this time.

    You should begin planning to replace ext/mysql with one of the other, more modern, extensions in order that you can reap the rewards of the benefits they offer; you might also use it as an opportunity to refactor your database access methods into a more modular structure.

    However, if you have an urgent need to upgrade PHP right away, you might consider suppressing deprecation errors for the time being: but first be sure to identify any other deprecation errors that are also being thrown.

• You are using a third party project that depends upon ext/mysql.

  Consider whether you really need to upgrade to PHP v5.5 at this time.

  Check whether the developer has released any fixes, workarounds or guidance in relation to this specific issue; or, if not, pressure them to do so by bringing this matter to their attention. If you have an urgent need to upgrade PHP right away, you might consider suppressing deprecation errors for the time being: but first be sure to identify any other deprecation errors that are also being thrown.

  It is absolutely essential to perform regression testing.