mysql query id as variable not working - php

Question

I want to update my MySQL table. When I type the ID as a number works, but when using a variable instead, it does not work.
What I am trying to do is order elements of an html table by column.
I have e.g. 4 Columns:
$colname = array("Column1", "Column2", "Column3", "Column4");
I get the IDs of the elements already sorted from the URL variable:
$strTaskIds = $_GET["taskIds"];
// for example: $strTaskIds = "3;1;32_4;5_6;36_34;7"
Now I split the string into a 2D-Array and update the MySQL table:
$arrTaskIds = explode("_", $strTaskIds);
for($i = 0; $i < count($arrTaskIds); $i++) {
$arrIdsPerCol = explode(";", $arrTaskIds[$i]);
for($j = 0; $j < count($arrIdsPerCol); $j++) {
$sql = "UPDATE tasks SET col='$colname[$i]', rank=$j WHERE id=$arrIdsPerCol[$j]";
}
if($conW->query($sql) === TRUE) {
$error = 0;
} else {
$error = 1;
}
}
When I write a number E.G 7 instead of the variable $arrIdsPerCol[$j] it works.
Writing (int)$arrIdsPerCol[$j] does not work either.

Answer 1

The reason i gave you no error message is that there was none. It just looked like the MySQL table is not updating.
After starring at my code for quite a long time a found the problem.
I placed the query() code in the outer loop. But i needed it in the inner loop.
Problem solved:
$arrTaskIds = explode("_", $strTaskIds);
$error = 0;
for($i = 0; $i < count($arrTaskIds); $i++) {
$arrIdsPerCol = explode(";", $arrTaskIds[$i]);
for($j = 0; $j < count($arrIdsPerCol); $j++) {
$sql = "UPDATE tasks SET col='$colname[$i]', rank=$j WHERE id=$arrIdsPerCol[$j]";
if($conW->query($sql) === TRUE) {
} else {
$error = 1;
}
}
}