Hi all! I found the resolved topic about custom dialect https://forum.phalcon.io/discussion/17641/bitcount-not-supported-by-phalcon. I tried the solution there and i've came across with a few questions.

  1. OP code snippet contained BITWISE XOR operator (^) howerver Phalcon does not contain that operator, does it? So I had to create custom function like so: 
    $dialect->registerCustomFunction(
    'BITWISE_XOR',
    function($dialect, $expression) {
        return sprintf(
            '%d ^ %d',
            $dialect->getSqlExpression($expression['arguments'][0]),
            $dialect->getSqlExpression($expression['arguments'][1])
        );
    }
);
  2. The proposed solution by corentin-begne does not seem to work for me. Here is my test. If I do this query in mysql cli: 
    SELECT MAX(BIT_COUNT(1222+5666)) from Temp;

    the result is: 7. If i do the same query in phalcon:

    $phql = "SELECT MAX( BIT_COUNT( 1222 + 5666 ) ) from Temp";
$query = $this->modelsManager->createQuery($phql);
$r = $query->execute();
print_r($r->getLast());

    the result is :

    Phalcon\Mvc\Model\Row Object
(
[0] => 5
)

    However if I change custom function sprintf from %d to %s like so:

    $dialect->registerCustomFunction(
        'BIT_COUNT',
        function($dialect, $expression) {
            return sprintf(
                'BIT_COUNT(%s)',
                $dialect->getSqlExpression($expression['arguments'][0])
            );
        }
);

    the result is like it should be:

    Phalcon\Mvc\Model\Row Object
(
[0] => 7
)

Also I tried to specify types for the binding variables like {number:int} but it does not help either.

Help please. Thanks in advance!