$php_compat = version_compare( $php_version, $required_php_version, '>=' );
$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );
$php_compat = version_compare( $php_version, $required_php_version, '>=' );
$mysql_compat = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );