PHP writing out PNGs, consistent problem in IE8

If I call: http://localhost/info/imgfeed.php?img=deer.png in the IE address bar then it is displayed fine.

If I link the URLs in an HTML file like this:开发者_如何学Go

<img src="imgfeed.php?img=dove.png" alt="" height="" width="" />
<img src="imgfeed.php?img=dolphin.png" alt="" height="" width="" />
<img src="imgfeed.php?img=deer.png" alt="" height="" width="" />

Then it fails miserably on IE but works fine on other browsers (tested Chrome/FF in newest stable releases). My PHP code is as follows (almost verbatim copy from PHP manual):

<?php
$server = $_SERVER['DOCUMENT_ROOT'];
$path = basename(dirname(__FILE__));
write_img($server.'/'.$path.'/'.$_GET["img"]);

function write_img($filename) {
  $size = getimagesize($filename);
  if ($size && $fp) {
    header("Content-type: {$size['mime']}");
    header("Cache-Control: no-cache");
    header("Expires: -1");
    readfile($filename);
    exit;
  } else {
    // error
  }
}
?>

Any ideas as to what is going on would be highly appreciated, i tried a range of tricks with headers as well as with .htaccess (making the PHP file appear as a PNG) but none of this has any effect on rendering in IE which ultimately only ever shows 3 minuscule dots (that can be saved as untitled.bmp).

Update problem solved courtesy of Meagar (remove width/height from HTML and all is good). Example above updated to reflect advice from Marc B on fpassthru vs readfile.

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Have you tried omitting the width and height attributes for your <img> tag? The server-side code is almost certainly fine; IE is likely interpreting width="" as width="0" and displaying the tiny dots you mentioned.

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You could try adding some more headers which sometimes seem to fix IE issues:

header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");

But as meagar says, IE6 doesn't like blank width and height attributes, and always requires a value in there.

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have you tried using

imagepng($output);

for rendering the image?

also it can help to use

ob_clean();
flush();

before fpassthru($fp); to clean the buffer before rendering.