How to use mysql_* functions in PHP?

First, let's begin with the standard comment we give everyone:

Please, don't use mysql_* functions in new code. They are no longer maintained and are officially deprecated. See the red box? Learn about prepared statements instead, and use PDO orMySQLi - this article will help you decide which. If you choose PDO, here is a good tutorial.

Let's go through this, sentence by sentence, and explain:

• They are no longer maintained, and are officially deprecated
  This means that the PHP community is gradually dropping support for these very old functions. They are likely to not exist in a future (recent) version of PHP! Continued use of these functions may break your code in the (not so) far future.
  NEW! - ext/mysql is now officially deprecated as of PHP 5.5!

  Newer! ext/mysql has been removed in PHP 7

• Instead, you should learn of prepared statements -
  mysql_* extension does not support prepared statements, which is (among other things) a very effective countermeasure against SQL Injection. It fixed a very serious vulnerability in MySQL dependent applications which allows attackers to gain access to your script and performany possible query on your database.
  For more information, see How can I prevent SQL-injection in PHP?
• See the Red Box?
  When you go on any mysql function manual page, you see a red box, explaining it should not be used anymore.
• Use either PDO or MySQLi
  There are better, more robust and well built alternatives, PDO - PHP Database Object, which offers a complete OOP approach to database interaction, and MySQLi, which is a MySQL specific improvement.

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