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POCaching image requests through PHP - If-Modified-Since not being sent
 

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    <p>I am serving images through php and having some problems setting it up to respond with 304 headers to save on load time.</p> <p>Most of the code below I found on php.net. It works, however ALWAYS responds with 200. <strong>For some reason the If-Modified-Since header is not being received on any requests even though I am sending the Last-Modified header initially.</strong> This is being done on an apache server. Any idea what might be wrong?</p> <p><a href="http://louiswalch.com/beta/304_test/" rel="noreferrer">Example here.</a></p> <p>This page will load the image from disk and display it to browser, along with sending a Last-Modified header. If you refresh the page, the browser doesn't send a If-Modified-Since header like it should.</p> <pre><code>define('SITEPATH', (dirname($_SERVER['SCRIPT_NAME']) == '/') ? '/' : dirname($_SERVER['SCRIPT_NAME']).'/'); $load_path = $_SERVER['DOCUMENT_ROOT'] . SITEPATH . 'fpo_image.jpg'; // Get headers sent by the client. $headers = apache_request_headers(); $file_time = filemtime($load_path); header('Cache-Control: must-revalidate'); header('Last-Modified: '.gmdate('D, d M Y H:i:s', $file_time).' GMT'); if (isset($headers['If-Modified-Since']) &amp;&amp; (strtotime($headers['If-Modified-Since']) == $file_time)) { header('HTTP/1.1 304 Not Modified'); header('Connection: close'); } else { header('HTTP/1.1 200 OK'); header('Content-Length: '. filesize($load_path)); header('Content-type: image/jpeg'); readfile($load_path); } </code></pre>
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    1. USLouis W
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    1. CO+1 for question! A very similar problem with If-Modified Since header returning the full content instead of 304: http://stackoverflow.com/questions/4810806/cached-php-generated-thumbnails-load-slow-how-to-find-problem-solution-from-wat
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