For users confused about getting "1" as a return value from ob_get_level at the beginning of a script: this likely means the PHP ini directive "output_buffering" is not set to off / 0. PHP automatically starts output buffering for all your scripts if this directive is not off (which acts as if you called ob_start on the first line of your script).
If your scripts may end up on any server and you don't want end-users to have to configure their INI, you can use the following at the start of your script to stop output buffering if it's already started:
<?php
if (ob_get_level()) ob_end_clean();
?>
Alternatively, you can use the opposite if you always want to have an output buffer at the start of your script:
<?php
if (!ob_get_level()) ob_start();
?>
ob_get_level
(PHP 4 >= 4.2.0, PHP 5, PHP 7, PHP 8)
ob_get_level — Return the nesting level of the output buffering mechanism
Elenco dei parametri
Questa funzione non contiene parametri.
Valori restituiti
Returns the level of nested output buffering handlers or zero if output buffering is not active.
Attenzione
The value for identical levels between ob_get_level()
and ob_get_status() is off by one.
For ob_get_level()
the first level is 1.
Whereas for ob_get_status()
the first level is 0.
Vedere anche:
- ob_start() - Turn on output buffering
- ob_get_status() - Get status of output buffers
- ob_get_contents() - Return the contents of the output buffer
add a note
User Contributed Notes 5 notes
Anonymous ¶
12 years ago
Anonymous ¶
9 years ago
This can be used to handle exceptions properly when using output buffering for rendering a view which may or may not be using output buffering
<?php
function getView($view)
{
$level = ob_get_level();
ob_start();
try
{
include $view;
}
catch (Exception $e)
{
while (ob_get_level() > $level)
{
ob_end_clean();
}
throw $e;
}
return ob_get_clean();
}
bonzini at gnu dot org ¶
20 years ago
Even under older PHP, you can decide if output buffering is active (i.e. ob_get_level() > 0) using
<?php $ob_active = ob_get_length () !== FALSE ?>
Paolo
mark dot richards at massmicro dot com ¶
12 years ago
It was noted that ob_get_level() reports 1 prior to starting buffering, and in php 5.3.6-13 I can confirm this:
<?php
echo ob_get_level(); // --> 1
?>
It seems an internal counter for the output buffering needs to be initialized. To start things off properly, this appears to do:
<?php
ob_end_clean();
echo ob_get_level(); // --> 0
?>
Anonymous ¶
19 years ago
Sometimes, ob_get_level() may be off by 1 because at the start of the script, it will return 1 even if ob_start() has never been called (and clearing the output buffer via ob_end_clean() and the like can be done without error). As a result, the first ob_start() will have an ob_get_level() of 2, the second will be 3, and so on.
I'm not sure if this is a PHP 5 thing or [if it's related to when a] server is set to gzip all html documents.
Also, up until at least PHP 5.0.4 (current version), ob_get_level() will always return 0 inside a destructor. This happens because the garbage collection for output buffers has already done before the destructor is called. If you want to do something with the output buffer from within an object before the script exits, using a callback function with ob_start() is the way to go.
