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POHow to suppress/remove PHP session cookie
 

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  1. POHow to suppress/remove PHP session cookie
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    <p>I need to suppress an already set session cookie header, but I cannot find any way to do this.</p> <p><strike>Why?<br> I need to make an image, sent by a PHP script, cacheable by the end user; this image is used to track if a newsletter has been read by the receiver, so if the image is requested I know the newsletter has been read. I only need to know when the newsletter gets opened for the first time, the subsequent requests can be ignored. The problem is that, even if I properly set the Expire and Cache-Control headers, the image is requested every time the user opens the newsletter--only that image used for the tracking--basically because it's not cached by the user. I used this <a href="http://www.ircache.net/cgi-bin/cacheability.py" rel="nofollow noreferrer">tool</a> to understand why the URL is not cacheable, and it says because of the cookie sent.</p> <p>What I want to avoid is the user seeing a delay on the load of the tracking image.</strike></p> <p>So I have a <code>session_start()</code> in my website init function, that I don't want to remove, because the website is big and complicated, and making some radical change like starting the session only if needed (one of the solutions I envisioned) is not desirable. Calling <code>session_start()</code> sets the <code>Set-Cookie:</code> header with the <code>PHPSESSID</code> cookie, and I need to remove it. Reading from the <code>header()</code> page on php.net I tried setting it with an empty value like this</p> <pre><code>header('Set-Cookie:'); header('Set-Cookie:', true); header('Set-Cookie: '); header('Set-Cookie: ', true); </code></pre> <p>before and after a call to <code>session_write_close()</code>, but all I obtained is that the user receives a <code>Set-Cookie:</code> header, without any value, exactly as written in the <code>header</code> function argument.</p> <p>I must say I'm still using PHP 5.2, so I cannot use the <code>header_remove()</code> function I see in the manual, and lighttpd 1.4.24.</p> <p><strong>EDIT:</strong> so, it seems the tool I used to check my headers is not that good. I looked at the headers with <code>curl --head</code> and saw the headers below.</p> <pre><code>HTTP/1.1 200 OK X-Powered-By: PHP/5.2.9 Set-Cookie: PHPSESSID=qn3ms55nvst2717e7b73qqu445; path=/ Last-Modified: Sun, 29 Mar 2009 21:53:36 GMT ETag: "cb1dffff8c10db7b0a88794b1453cab8" Expires: Sun, 20 Dec 2009 23:28:07 GMT Cache-Control: private, max-age=2592000 Pragma: no-cache Content-Type: image/png Content-Length: 1322 Date: Fri, 20 Nov 2009 23:28:07 GMT Server: lighttpd/1.4.24 </code></pre> <p>As you see it is set a <code>Pragma: no-cache</code>. The tool I used said that the <code>Pragma</code> header is not used, but it was wrong. I tried setting <code>Pragma: cache</code>, and it made the mail client cache the image.</p> <p>I made another discovery, maybe the impossibility of unsetting the <code>Set-Cookie</code> header is because of lighttpd, since I cannot remove the <code>Pragma</code> header using <code>header('Pragma:')</code>. Looking forward to PHP 5.3. Can someone using Apache confirm that the above <code>header</code> call removes the <code>Pragma</code> header?</p> <p>Thanks txyoji for the enlightening comment :-)</p> <p>At this point it seems this question is here only to confirm lighttpd cannot remove headers by setting an header without value.</p>
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    1. COCan you show a complete list of headers sent in response to the dynamic image request. This tool will show a complete list of headers. https://addons.mozilla.org/en-US/firefox/addon/3829
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    2. COA nice tool that analyses your headers is http://redbot.org/. It can help figure out why a response it not being cached.
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      1. USMartijn Heemels
 

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