Cache headers

When you set a header via $this->output->set_header(), but also use caching via $this->output->cache(), those headers you sent will not be cached along with your content.

This can be very problematic: if you're caching CSS, for example, you want the cache to return that CSS along with the Content-Type header "text/css" - otherwise most browsers will interpret your CSS as just plain text, and hence not use it for rendering.

With a few simple alterations to the Output class, headers will also be cached and returned. This involved small changes to the _write_cache() and _display_cache() functions, shown below.

[b]_write_cache function, around line 300 (surrounding code also shown)[/b]

[code]// Implode all the headers into a newline-delimited string // String is prepended with a pseudo-header giving the expiration time $headers = "X-CI-Timestamp: " . (time() + ($this->cache_expiration * 60)) . "\n"; $headers .= implode("\n", $this->headers);

flock($fp, LOCK_EX); fwrite($fp, $headers . "\n\n" . $output); // This line changed flock($fp, LOCK_UN); fclose($fp); @chmod($cache_path, DIR_WRITE_MODE); [/code]

[b]_display_cache function, around line 360 (surrounding code also shown)[/b]

[code]// Seperate headers and cache list($headers, $cache) = explode("\n\n", $cache, 2);

// Get each header as an array item $headers = explode("\n", $headers); foreach ($headers as $header) { // Is this header the timestamp pseudo-header? if (FALSE === strpos($header, "X-CI-Timestamp: ")) { $this->set_header($header); // No, it's not: set the header } else { // Has the file expired? If so we'll delete it. $timestamp = substr($header, strlen("X-CI-Timestamp: ")); if (time() >= trim($timestamp)) {
@unlink($filepath); log_message('debug', "Cache file has expired. File deleted"); return FALSE; } } }

// Display the cache $this->_display($cache); // This line changed [/code]

These additions automatically write headers into the cache and incorporate the timestamping in the same mechanism.

This code is given for demonstration; it could be cleaned up, by, for instance, adding a variable holding the timestamp pseudo-variable identifier, so that it needn't be repeated, and one for the delimiters too.

We can now remove:

[b]Lines 103 and 104[/b]

[code]/*

• Note: If a file is cached, headers will not be sent. We need to figure out
• how to permit header data to be saved with the cache data... */[/code]