filled polygon does not render 129th time on same image

[Swan666]

I have a function which creates a polygon of blue color. I call this function inside a loop of 128 iterations. For every iteration, i change the value of x and y so that my polygon is rendered on new location. This goes fine and i get 128 new polygons on my image after running the script. But if change the number to 129, the 129th polygon is transparent or what i cannot guess.It just does not display or render at all. Is this a bug or some mistake with my code?

I am using php version 5.1.4 that came with WAMP5 Version 1.6.3

my code is -
[php]<?php
$im = imagecreate(600, 400);
$x = 20;
$y = 350;
for($i=1;$i<=128;$i++) //create a polygon 128 times
{
drawPoly($x,$y,$im);
$x = $x+2;
$y = $y-2;
}
header('Content-type: image/png');
imagepng($im);
imagedestroy($im);
function drawPoly($xCoord,$yCoord,$im)
{
$x1 = $x2 = $xCoord;
$x3 = $x4 = $xCoord + 70;
$y1 = $y4 = $yCoord;
$y2 = $y3 = $yCoord + 30;
$Poly = array(0 => $x1,1 => $y1,2 => $x2,3 => $y2,4 => $x3,5 => $y3,6

=> $x4,7 => $y4);
$bg = imagecolorallocate($im, 150, 150, 150);
$blue = imagecolorallocate($im, 0, 0, 255);
imagefilledpolygon($im, $Poly, 4, $blue);
}
?>[/php]

[ronverdonk]

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[Swan666]

The issue is solved. It was the problem with the code.

i took this line $bg = imagecolorallocate($im, 150, 150, 150); outside the function drawPoly(), and everything worked as

expected.

the new updated code is -

<?php
$im = imagecreate(600, 400);
$bg   = imagecolorallocate($im, 150, 150, 150);
$x = 20;
$y = 350;
for($i=1;$i<=150;$i++) //create a polygon 128 times
    {
        drawPoly($x,$y,$im);
        $x = $x+2;
        $y = $y-2;
    }
    header('Content-type: image/png');
    imagepng($im);
    imagedestroy($im);    
    function drawPoly($xCoord,$yCoord,$im)
    {
        $x1 = $x2 = $xCoord;
        $x3 = $x4 = $xCoord + 70;
        $y1 = $y4 = $yCoord;
        $y2 = $y3 = $yCoord + 30;
        $Poly = array(0  => $x1,1  => $y1,2  => $x2,3  => $y2,4  => $x3,5  => $y3,6  => $x4,7  => $y4);
        $blue = imagecolorallocate($im, 0, 0, 255);
        imagefilledpolygon($im, $Poly, 4, $blue);
    }
?>
 

But i still want to know why this happened and why it worked when i took that line outside the function?