Why does Wordpress say there is no MySQL extension?

Question

MySQL

Your PHP installation appears to be missing the MySQL extension which is required by WordPress.
This is the line I see when I try to run it. I myself use the PHP-FPM+nginx stack on Ubuntu 14.04. php5-mysql is installed, what else is there, I don't know. PHPMyAdmin works without showing off. PHP version 5.5.9.

Answer 1

if ( ! extension_loaded( 'mysql' ) && ! extension_loaded( 'mysqli' ) && ! file_exists( WP_CONTENT_DIR . '/db.php' ) ) {
    wp_load_translations_early();
     header( 'Content-Type: text/html; charset=utf-8' );
    die( __( 'Your PHP installation appears to be missing the MySQL extension which is required by WordPress.' ) );
  }