Image upload error

I need help, (in more ways than one), but thats another story

seriously tho, can someone please tell me what is wrong with this script

        if ($_POST['img_upload'] == 1)
{
	$mwidth = "100";
	$mheight = "150";

        $uploadedfile = $_FILES['userpic']['tmp_name'];
	$src = imagecreatefromjpeg($uploadedfile);

	echo "file: ".$uploadedfile."<br>";
	$size = getimagesize($uploadedfile);
	for($i=0;$i<6;$i++)
	{
   		echo "$i".$size[$i]."<br>";
	}
	$width = $size[0];
	$height = $size[1];
	echo "w".$width."<br>";
	echo "h".$height."<br>";

        if ($height > $width)
	{
		$newheight = $mheight;
		$newwidth = ($height/$width)*$mwidth;
	}
	else
	{
		$newwidth = $mwidth;
		$newheight = ($width/$height)*$mheight;
	}

	$tmp = imagecreatetruecolor($newwidth,$newheight);
	imagecopyresampled($tmp,$src,0,0,0,0,$newwidth,$newheight,$width,$height);

	$imgurl = md5($row_user['username']);
	$filename = "images/userpictures".$imgurl;
	imagejpeg($tmp,$filename,100);
	imagedestroy($src);
	imagedestroy($tmp);
} 

PHP:

the error messages i get is

the code begins at line 91 and ends at 129.

I haven't written this code, i'm not a php programmer, but it was written FOR me, the guy that wrote it has gone awol

please help.

Laz