PHP: Runtime Configuration

Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

The zlib extension offers the option to transparently compress your pages on-the-fly, if the requesting browser supports this. Therefore there are three options in the configuration file php.ini.

**Zlib Configuration Options**
Name	Default	Changeable
zlib.output_compression	"0"	`INI_ALL`
zlib.output_compression_level	"-1"	`INI_ALL`
zlib.output_handler	""	`INI_ALL`

For further details and definitions of the INI_* modes, see the Where a configuration setting may be set.

Here's a short explanation of the configuration directives.

zlib.output_compression bool/int

Whether to transparently compress pages. If this option is set to "On" in php.ini or the Apache configuration, pages are compressed if the browser sends an "Accept-Encoding: gzip" or "deflate" header. "Content-Encoding: gzip" (respectively "deflate") and "Vary: Accept-Encoding" headers are added to the output. In runtime, it can be set only before sending any output.

This option also accepts integer values instead of boolean "On"/"Off", using this you can set the output buffer size (default is 4KB).

Note:
output_handler must be empty if this is set 'On' ! Instead you must use zlib.output_handler.

zlib.output_compression_level int

Compression level used for transparent output compression. Specify a value between 0 (no compression) to 9 (most compression). The default value, -1, lets the server decide which level to use.

zlib.output_handler string

You cannot specify additional output handlers if zlib.output_compression is activated here. This setting does the same as output_handler but in a different order.

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User Contributed Notes 5 notes

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-1

finlanderid at gmail dot com ¶

9 years ago


Does anyone find these two statements contradictory? Am I not understanding something, or are these statements actually contradicting each other? 

Statement ONE from output_handler:
"output_handler must be empty if this [zlib.output_compression] is set 'On' ! Instead you must use zlib.output_handler."

Statement TWO from zlib.output_handler:
"You cannot specify additional output handlers if zlib.output_compression is activated ..."

Statement ONE says you have to use zlib.output_handler, if zlib.output_compression is turned ON. Statement TWO says that, if zlib.output_compression is turned ON, you cannot use zlib.output_handler. 

what the heck?

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-5

scott at pawprint dot net ¶

12 years ago


In the hopes this will help others - a hard to spot gotcha when implementing zlib.output_compression. if you use flush() anywhere in your script (even right at the end) the compression won't work - you need to let that happen automatically or it ends up being sent uncompressed.

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-5

Anon ¶

5 years ago


Because of possible BREACH attacks when using output compression cross-site scripting should be disallowed. This can be achieved with the same-site cookie attribute:

https://www.sjoerdlangkemper.nl/2016/04/14/preventing-csrf-with-samesite-cookie-attribute/

https://caniuse.com/#feat=same-site-cookie-attribute

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-7

pacerier+php dot net at gmail dot com ¶

7 years ago


@finlanderid, Exactly. As output_handler and zlib.output_handler cant be both set (as per ""<output_handler must be empty if this is set 'On'>""), "different order" refers to?

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-15

galaxy ¶

9 years ago


finlanderid at gmail dot com,

you are mixing two separate things and consider them to be the same thing, hence the confusion.

There are two output_handlers:

1. http://php.net/manual/en/outcontrol.configuration.php#ini.output-handler

2. http://php.net/manual/en/zlib.configuration.php#ini.zlib.output-handler

Now, if you re-read your quotes again with this information it won't be confusing anymore :)

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