Array sent via Json for Javascript comes null on it

Question

I have an application where, a Javascript I have a function that performs an Ajax call to the file . php handle. The . php handles the function buscaConta(p) like: makes a SELECT in the Mysql database (managed via XAMPP and phpMyAdmin), takes the result of this query, saves in an array and returns to another Javascript function (callback), called "formaCanvas(p)" in Json format. Only that what I get in this callback JS function is [] . What would be a correct empty array? That most of the time. Only the first time I run the application after it is loaded do I get the correct result on it: the agency, account and balance number. . That would be a correct empty array?

Only that function search engine() php, before sending the query result to formaCanvas from JS, I test this query result, and it is an array filled with values...

Why it arrives empty for the function formaCanvas() J? Where am I wrong? Javascript function containing Ajax call:

function formaQueryConta(cpf){

        var numConta= jsonDtContasCliente[(document.getElementById("listaContas").value)-1];
        var parms = "&cpf="+cpf+"&conta="+numConta;
        ajaxCall("Persistencia.php?action=buscaConta" +parms, formaCanvas);

    }

All right in the above function.

Ajaxcall function:

function ajaxCall(stringCall, callback){
var httpRequest = new XMLHttpRequest;

    httpRequest.onreadystatechange = function(){
        if (httpRequest.readyState === 4) {
            if (httpRequest.status === 200) {
              callback(httpRequest.responseText);

            }
        }
    };
    httpRequest.open('GET', stringCall);
    httpRequest.send();

}

Now Handler of Ajax calls in my . php:

if(@$_REQUEST['action'] == 'buscaConta')
    {
     buscaConta();

    }

Everything’s fine with Handler at first. Now, the function " searchConta(); ":

 function buscaConta(){

        $con = ConectaDB();
        $cpf = $con->real_escape_string($_REQUEST['cpf']);
        $conta = $con->real_escape_string($_REQUEST['conta']);
        $cpf = extraiSoNumsDeString($cpf); 

        $result = mysqli_query($con, "SELECT agencia,conta,saldo FROM contas WHERE dono='$cpf' AND conta='$conta' ORDER BY agencia");
        $retData = Array();
        $x=0;
        while( $row = mysqli_fetch_array($result, MYSQLI_NUM)){
            print_r($row);
            $retData[] = $row[0];

           }
            $con->close();  
        echo json_encode($retData);

    }
        }

Extra functionSoNumsDeString($Cpf):

There’s nothing wrong with it, it returns a string of numbers.

Function organizationResultDaQuery($result); At first everything is fine with it

function organizaResultQuery($result){
            $retData = Array();
            while( $row = mysqli_fetch_array($result, MYSQLI_NUM)){

            $retData[] = $row[0];
            }

            return $retData;
        }

HERE APPEARS THE PROBLEM: AJAX CALL’s CALLBACK FUNCTION THAT RECEIVES THE RESULTING QUERY ARRAY FROM PHP. THE ARRAY ARRIVES HERE EMPTY...

On it, I simply print on the screen the query result.:

function formaCanvas(res){

    console.log("Retorno da busca completa da conta: " +res);
}

The table searched in mysql:

I spent almost an hour debugging and I can’t fix it. Thanks already!