<?php

$arr = array();

$q1 = 1;
$q2 = 2;
$q3 = 3;
$q4 = 4;
$q5 = 5;

for($i=1; $i<=5; $i++)
{
    $arr[] = ${"q".$i}; 
}

$str = implode($arr, ',');

print_r($str);

1,2,3,4,5