Since PHP 5.5, mysql_connect() extension is deprecated. Now it is recommended to use one of the 2 alternatives.
PHP mysqli_connect() function is used to connect with MySQL database. It returns resource if connection is established or null.Syntax
resource mysqli_connect (server, username, password)
PHP mysqli_close() function is used to disconnect with MySQL database. It returns true if connection is closed or false.Syntax
bool mysqli_close(resource $resource_link)