The definition should mention that the function also "turns off output buffering", not just cleans it.
(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
ob_get_clean — Get 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,
returns the contents of the active output buffer
and turns off the active output buffer.
ob_get_clean() will fail
without an active output buffer started with the
PHP_OUTPUT_HANDLER_REMOVABLE flag.
ob_get_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.
Returns the contents of the active output buffer on success
or false on failure.
ob_get_clean() will return false
but will not generate an E_NOTICE
if there is no active output buffer.
If the function fails it generates an E_NOTICE.
Example #1 A simple ob_get_clean() example
<?php
ob_start();
echo "Hello World";
$out = ob_get_clean();
$out = strtolower($out);
var_dump($out);
?>The above example will output:
string(11) "hello world"
The definition should mention that the function also "turns off output buffering", not just cleans it.Also, don't forget that you will need to ob_start() again for any successive calls:
<?php
ob_start();
echo "1";
$content = ob_get_clean();
ob_start(); // This is NECESSARY for the next ob_get_clean() to work as intended.
echo "2";
$content .= ob_get_clean();
echo $content;
?>
Output: 12
Without the second ob_start(), the output is 21 ...Keep in mind that output may be buffered by default, depending on how you are running PHP (CGI, CLI, etc.). You can use ob_get_level() to determine if an output buffer has already been started. On most web servers I've used, output buffering is already one level deep before my scripts start running.
You should only end as many output buffers as you start. Assuming that your buffer is always the first buffer, or otherwise closing pre-existing buffers, could lead to problems. In PHP 5.5, you can ensure that output buffers are ended properly using a try-finally block.
Something like this is almost guaranteed to break stuff:
<?php
// Don't ever do this!
while (ob_get_level() > 1)
{
ob_end_flush();
}
$content = ob_get_clean();
?>
The problem is that number, "1". Using a fixed number there is asking for trouble. Instead, use ob_get_level() to get the number of output buffers applied when your code starts, and return to that number, if you really must use an unknown number of output buffers:
<?php
ob_start();
$saved_ob_level = ob_get_level();
// Do stuff here:
run_something();
// If you really must close all of your output buffers except one, this'll do it:
while (ob_get_level() > $start_ob_level)
{
ob_end_flush();
}
// And now, the final output buffer that belongs to us:
$content = ob_get_clean();
?><?php
ob_start();
echo "1";
$content = ob_get_clean();
echo "2";
$content .= ob_get_clean();
echo $content;
?>
This script outputs 21 in CLI mode and 12 otherwise (under my apache and nginx)I was trying to debug my code using error_log() and I discovered that ob_get_clean() also truncates the error_log() buffer right in the middle of its output, and well as the output buffer which it is supposed to truncate. If you are using error_log(), use ob_get_contents() and ob_end_clean() instead of ob_get_clean().