Does Drupal work with PHP 7? I have working development project of Drupal 7 using PHP 5.x. I changed the PHP version to PHP 7 using nginx webserver. It does not work and I have got the following error message:

 Fatal error: Uncaught Error: Undefined class constant
 'MYSQL_ATTR_USE_BUFFERED_QUERY' in
 C:\xampp-2\htdocs\d738\includes\database\mysql\database.inc:46 Stack
 trace: #0 C:\xampp-2\htdocs\d738\includes\database\database.inc(1689):
 DatabaseConnection_mysql-&gt;__construct(Array) #1
 C:\xampp-2\htdocs\d738\includes\database\database.inc(1479):
 Database::openConnection('default', 'default') #2
 C:\xampp-2\htdocs\d738\includes\database\database.inc(2570):
 Database::getConnection() #3
 C:\xampp-2\htdocs\d738\includes\cache.inc(348):
 db_escape_table('cache_bootstrap') #4
 C:\xampp-2\htdocs\d738\includes\cache.inc(329):
 DrupalDatabaseCache-&gt;getMultiple(Array) #5
 C:\xampp-2\htdocs\d738\includes\cache.inc(56):
 DrupalDatabaseCache-&gt;get('module_implemen...') #6
 C:\xampp-2\htdocs\d738\includes\module.inc(723):
 cache_get('module_implemen...', 'cache_bootstrap') #7
 C:\xampp-2\htdocs\d738\includes\module.inc(892):
 module_implements('system_theme_in...') #8
 C:\xampp-2\htdocs\d738\modules\system\system.module(2502):
 module_invoke_all('system_theme in
 C:\xampp-2\htdocs\d738\includes\database\mysql\database.inc on line 46


This error means that Drupal 7 is using obsoleted MySQL functions and it is not support with PHP any more!

However, I don't think Drupal still uses this obsoleted PHP extension. So I have a strange error as I think!
Search and edit your php.ini file, you must search this line:

;extension=php_pdo_mysql.dll


remove the ; and save the file, then restart your webserver.