Passing an array from PHP to JavaScript using JSON

H guys.

I have seen that some people already had a similar problem but by reading those posts i couldnt get my problem solve. I have an array in PHP (IQ_PHP_MODB_v4.php) whose values can be echoed and are valid (so i suppose that the php is al right.) my javascript file uses json to get the array created by PHP file. The php part of code that calls json encode is:

 $out[1]=$data;
 $out[2]=$leitura1;
 $out[3]=$leitura2; 
 echo json_encode($out);

The javascript part of code that calls json is:

$.ajax({
    type: 'GET',
        url: 'IQ_PHP_MODB_v4.php',
        async: false,
        dataType: 'json',
        success: function(data) {

        document.write("succes");
        var tensaoValor = eval(data[2]);
        var correnteValor = eval(data[3]);
        var potenciaValor = eval(data[1]);
        var potenciaRValor = 230;
    }
    });

I can´t understand why JSON cant get the variable. The word succedd is never printed so i suppose that the data does not arrive to javascipt. Does anyone have an idea how to fix this? i am stucked with this since the beggining of the week.

Thanks in advance