Meta OR
$meta_query = array( 'relation' => 'OR', array( 'key' => 'market_center_fields_ar_city', 'value' => '$city', ), array( 'key' => 'market_center_fields_city', 'value' => '$city', ), );
$meta_query = array( 'relation' => 'OR', array( 'key' => 'market_center_fields_ar_city', 'value' => '$city', ), array( 'key' => 'market_center_fields_city', 'value' => '$city', ), );