How to disable output buffering in PHP
Do two things:
Disable the userspace output buffer, either...
Globally, by either...
- Turning off
output_bufferingin your php.ini, or
output_bufferingin your Apache config using
php_flag "output_buffering" Off
- Turning off
or for just the script you care about, by either...
Also, disable the server-level output buffer as much as you possibly can, by either:
ob_implicit_flush()at the start of your script, or
echostatement or other statement that adds output to the response body
Confusingly, there are two layers of buffering that may be relevant and the PHP documentation does a poor job of distinguishing between the two.
The output buffer
The first layer is usually referred to by the PHP docs as the 'output buffer'. This layer of buffering only affects output to the body of the HTTP response, not the headers. You can turn on output buffering with
ob_start(), and turn it off with
ob_end_clean(). You can also have all your scripts automatically start with output buffering on using the
output_buffering option in php.ini.
The default value of this option for production versions of php.ini is 4096, which means that the first 4096 bytes of output will be buffered in the output buffer, at which point it will be flushed and output buffering is turned off.
You can disable this layer of buffering globally by setting
Off in your php.ini file (or using
php_flag "output_buffering" Off
in your Apache config, if you're using Apache). Alternatively, you can disable it for a single script by calling
ob_end_flush() at the start of the script.
The write buffer, and the webserver buffer
Beyond the output buffer is what the PHP manual refers to as the 'write buffer', plus any buffering system your web server has. If you're using PHP with Apache through
mod_php, and are not using
mod_gzip, you can call
flush() to flush these; with other backends, it might work too, although the manual is cagey about giving assurances:
void flush ( void )
Flushes the write buffers of PHP and whatever backend PHP is using (CGI, a web server, etc). This attempts to push current output all the way to the browser with a few caveats.
flush() may not be able to override the buffering scheme of your web server and it has no effect on any client-side buffering in the browser. It also doesn't affect PHP's userspace output buffering mechanism. This means you will have to call both ob_flush() and flush() to flush the ob output buffers if you are using those.
There are also a couple of ways you can make PHP automatically call
flush() every time you
echo anything (or do anything else that echoes output to the response body).
The first is to call
ob_implicit_flush(). Note that this function is deceptively named; given its
ob_ prefix, any reasonable person would expect that it would affect the 'output buffer', as do
ob_flush etc. However, this is not the case;
flush(), affects the server-level output buffer and does not interact in any way with the output buffer controlled by the other
The second is to globally enable implicit flushing by setting the
implicit_flush flag to
On in your php.ini. This is equivalent to calling
ob_implicit_flush() at the start of every script. Note that the manual advises against this, cryptically citing "serious performance implications", some of which I explore in this tangentially related answer.
Prevent output buffering with PHP and Apache
The only solution that worked for me was to set the
output_buffering directive in php.ini to "Off". I didn't want to do this for the entire server, just this one specific resource. Normally you could use
ini_set from the PHP script, but for whatever reason php doesn't allow
output_buffering to be set in this way (see the php manual).
Well it turns out that if you're using Apache, you can set some php ini directives (including
output_buffering) from your server config, including a .htaccess file. So I used the following in a .htaccess file to disable the output_buffering just for that one file:
php_value output_buffering Off
And then in my static server configuration, I just needed
AllowOverride Options=php_value (or a larger hammer, like
AllowOverride All) in order for that to be allowed in a .htaccess file.
How to disable output buffering in nginx for PHP application
First php has to correctly flush everything :
Then, I found two working solutions:
1) Via Nginx configuration:
2) Via HTTP header in the php code
Disabling output buffering in PHP
You're only sending a small amount of data. Browsers have their own buffer, which can be based on a number of bytes, by which elements have been received, or by something else.
In short, there is nothing you can do about this. The buffering is happening client-side, not server-side. You could try sending more data before your
You can prove this by packet sniffing the connection between the server and the browser, with Wireshark or similar.
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