PHP imagecreatefromjpeg没有错误，没有图像

Question

我正在使用此代码

<?php

$sImagePath = $_GET["file"];

$iThumbnailWidth = (int)$_GET['width'];
$iThumbnailHeight = (int)$_GET['height'];
$iMaxWidth = (int)$_GET["maxw"];
$iMaxHeight = (int)$_GET["maxh"];

if ($iMaxWidth && $iMaxHeight) $sType = 'scale';
else if ($iThumbnailWidth && $iThumbnailHeight) $sType = 'exact';

$img = NULL;

$sExtension = strtolower(end(explode('.', $sImagePath)));
if ($sExtension == 'jpg' || $sExtension == 'jpeg') {

    $img = @imagecreatefromjpeg($sImagePath)
        or die("Cannot create new JPEG image");

} else if ($sExtension == 'png') {

    $img = @imagecreatefrompng($sImagePath)
        or die("Cannot create new PNG image");

} else if ($sExtension == 'gif') {

    $img = @imagecreatefromgif($sImagePath)
        or die("Cannot create new GIF image");

}

if ($img) {

    $iOrigWidth = imagesx($img);
    $iOrigHeight = imagesy($img);

    if ($sType == 'scale') {

        // Get scale ratio

        $fScale = min($iMaxWidth/$iOrigWidth,
              $iMaxHeight/$iOrigHeight);

        if ($fScale < 1) {

            $iNewWidth = floor($fScale*$iOrigWidth);
            $iNewHeight = floor($fScale*$iOrigHeight);

            $tmpimg = imagecreatetruecolor($iNewWidth,
                               $iNewHeight);

            imagecopyresampled($tmpimg, $img, 0, 0, 0, 0,
            $iNewWidth, $iNewHeight, $iOrigWidth, $iOrigHeight);

            imagedestroy($img);
            $img = $tmpimg;
        }     

    } else if ($sType == "exact") {

        $fScale = max($iThumbnailWidth/$iOrigWidth,
              $iThumbnailHeight/$iOrigHeight);

        if ($fScale < 1) {

            $iNewWidth = floor($fScale*$iOrigWidth);
            $iNewHeight = floor($fScale*$iOrigHeight);

            $tmpimg = imagecreatetruecolor($iNewWidth,
                            $iNewHeight);
            $tmp2img = imagecreatetruecolor($iThumbnailWidth,
                            $iThumbnailHeight);

            imagecopyresampled($tmpimg, $img, 0, 0, 0, 0,
            $iNewWidth, $iNewHeight, $iOrigWidth, $iOrigHeight);

            if ($iNewWidth == $iThumbnailWidth) {

                $yAxis = ($iNewHeight/2)-
                    ($iThumbnailHeight/2);
                $xAxis = 0;

            } else if ($iNewHeight == $iThumbnailHeight)  {

                $yAxis = 0;
                $xAxis = ($iNewWidth/2)-
                    ($iThumbnailWidth/2);

            } 

            imagecopyresampled($tmp2img, $tmpimg, 0, 0,
                       $xAxis, $yAxis,
                       $iThumbnailWidth,
                       $iThumbnailHeight,
                       $iThumbnailWidth,
                       $iThumbnailHeight);

            imagedestroy($img);
            imagedestroy($tmpimg);
            $img = $tmp2img;
        }    

    }

    header("Content-type: image/jpeg");
    imagejpeg($img);

}

?>

并且imagecreatefromjpeg适用于我的八张图片，但不适用于其中三张图片。它们是具有良好权限的Photoshop“save for web jpgs”。我没有收到错误，但我也没有在第33行“如果（$ img）”获得“真实”