What is my error in the very simple php?

What is my error in the very simple php?

i make a very simple php to check a data, but it not works.
<?php
$ngl="G";
if ($parsed[0][4]="0") {
$ngl="NG";
}
if ($parsed[0][5]="0") {
$ngl="NG";
}
?>
and the output of the
<?php echo $ngl; ?>
is always
G
But I know that $parsed[0][4] and $parsed[0][5] is 0. The problem is that
the output is G and not NG! I also tried to remove $ngl="G"; but then the
output is nothing.
What do I have to repair?
i just use = but == its the correct. thx all.