(PHP 4, PHP 5, PHP 7, PHP 8)
ob_end_clean — Clean (erase) the contents of the active output buffer and turn it off
This function calls the output handler
(with the PHP_OUTPUT_HANDLER_CLEAN and
PHP_OUTPUT_HANDLER_FINAL flags),
discards it's return value,
discards the contents of the active output buffer
and turns off the active output buffer.
ob_end_clean() will fail
without an active output buffer started with the
PHP_OUTPUT_HANDLER_REMOVABLE flag.
ob_end_clean()
will discard the contents of the active output buffer
even if it was started without the
PHP_OUTPUT_HANDLER_CLEANABLE flag.
This function has no parameters.
If the function fails it generates an E_NOTICE.
The following example shows an easy way to get rid of the contents of the active output buffer:
Example #1 ob_end_clean() example
<?php
ob_start();
echo 'Text that won\'t get displayed.';
ob_end_clean();
?>
Take note that if you change zlib output compression setting in between ob_start and ob_end_clean or ob_end_flush, you will get an error: ob_end_flush() failed to delete buffer zlib output compression
Example:
<?php
ob_start();
$output = ob_get_contents();
ini_set('zlib.output_compression', '1');
ob_end_clean();
?>
ob_end_clean(); in this example will throw the error.Note that if you started called ob_start with a callback, that callback will still be called even if you discard the OB with ob_end_clean.
Because there is no way of removing the callback from the OB once you've set it, the only way to stop the callback function from having any effect is to do something like:
<?php
$ignore_callback = false;
ob_start('my_callback');
...
if($need_to_abort) {
$ignore_callback = true;
ob_end_clean();
...
}
function my_callback(&$buffer) {
if($GLOBALS['ignore_callback']) {
return "";
}
...
}
?>If there is no confidence about output buffering (enabled or not),
you may try these guards:
<?php
while (ob_get_level() !== 0) {
ob_end_clean();
}
// or
while (ob_get_length() !== false) {
ob_end_clean();
}
?>You might want to prevent your script from executing if the client already has the latest version.
You can do it like so:
ob_start();
$mtime=filemtime($_SERVER["SCRIPT_FILENAME"])-date("Z");
$gmt_mtime = date('D, d M Y H:i:s', $mtime) . ' GMT';
$headers = getallheaders();
if(isset($headers["If-Modified-Since"])) {
if ($headers["If-Modified-Since"] == $gmt_mtime) {
header("HTTP/1.1 304 Not Modified");
ob_end_clean();
exit;
}
}
$size=ob_get_length();
header("Last-Modified: ".$gmt_mtime);
header("Content-Length: $size");
ob_end_flush();
Instead of checking the If-Modified-Since-Header against the date of the last modification of the script, you can of course query a database or take any other date that is somehow related to the modification of the result of your script.
You can for instance use this technique to generate images dynamically. If the user indicates he already has a version of the image by the If-Modified-Since-Header, there's no need to generate it and let the server finally discard it because the server only then interpretes the If-Modified-Since-Header.
This saves server load and shortens response-times.