(PHP 4, PHP 5, PHP 7)



ini_set ( string $varname , string $newvalue ) : string




不是所有有效的选项都能够用 ini_set() 来改变的。 这里有个有效选项的清单附录




成功时返回旧的值,失败时返回 FALSE


Example #1 设置一个 ini 选项

echo ini_get('display_errors');

if (!
ini_get('display_errors')) {



User Contributed Notes

ASchmidt at Anamera dot net 27-Jul-2017 11:29
When checking for the success of ini_set(), keep in mind that it will return the OLD value upon success - which may have been "0". Therefore you cannot just compare the return value - you have to check for "identity":


// This will NOT determine the success of ini_set(), instead
// it only tests if the old value had been equivalent to false
if ( !ini_set( 'display_errors', '1' ) )
    throw new \
Exception( 'Unable to set display_errors.' );

// This is the CORRECT way to determine success
if ( ini_set( 'display_errors', '1' ) === false )
    throw new \
Exception( 'Unable to set display_errors.' );   


This explains reported situations where ini_set() "always" seems to fail!
Gev 17-Jul-2017 06:57
ini_set('display_errors', 1);
Er.ellison 13-Nov-2015 07:44
if u receive  an Error with generic like  :
Maximum execution time of 30 seconds exceeded

if u set ini_set(max_execution_time, 300);
your problem will be solved
pls note that the 300 , is 300 seconds , which means 5 minute  you can set another value !
w3dk 06-May-2015 05:21
Whilst most boolean settings can be disabled by passing '0', 'Off' or `No' (in fact anything that is not '1', 'On' or 'Yes' - not case-sentive) to ini_set(), it should be noted that ini_get() returns the literal string as set. So if you later want to check this setting by calling ini_get() and it's been set to 'Off' (a non-empty string that evaluates to True), then you'll have to specifically check for this in a (case-insensitive) string comparison, rather than the simpler:

if (ini_get('config_setting')) { /* ... */ }

So, if you need to disable boolean settings I think it's preferable to set them to '0' (which simply evaluates to False).
nl-x 17-Sep-2014 11:32
I have experienced on some systems that ini_set() will fail and return a false, when trying to set a setting that was set inside php.ini inside a per-host setting. Beware of this.
anonymous 10-Aug-2014 04:30
Note that this function only works with PHP_INI_ALL options!
williamprogphp at yahoo dot com dot br 10-Jan-2014 12:20
I figured out why php dont output errors such as an expected ';' on code and output a 500 error. Some server are configured to omit php errors on pages using the directive display_errors=Off;

In most cases, the server will output a 500 Internal Server Error instead of php error because of it.

To prevent this default you must set this directive directly in the php.ini file and the server will show you the php error properly. Setting ini_set('display_errors', true) on-the-fly wont work.
Nik 25-Nov-2013 05:44
How to get xdebug var_dump to show full object/array regardless to php,ini settings:

ini_set("xdebug.var_display_max_depth", -1);
ini_set("xdebug.var_display_max_children", -1);
ini_set("xdebug.var_display_max_data", -1);
Nathan 08-Nov-2011 08:56
Careful - in some cases, when setting zlib.output_compression to "On" via ini_set, PHP won't send the Content-type header and browsers will garble the output. Set it to the desired buffer size instead, which sends the correct header:

("zlib.output_compression", 4096);
MadJoker 12-Aug-2009 01:46
If you use gz_handler you might want to switch over to

This can be controlled via the ini_set control.

<?php ini_set('zlib.output_compression', 'Off'); ?>


<?php ini_set('zlib.output_compression', 'On'); ?>
daevid at daevid dot com 30-Oct-2006 05:19
Be careful with setting an output_handler, as you can't use ini_set() to change it. *sigh*

In my php.ini I have this for my web pages (and I want it):

  output_handler = ob_gzhandler

But this causes my command line scripts to not show output until the very end.

#!/usr/bin/php -q
('output_handler', 'mb_output_handler');
"\noutput_handler => " . ini_get('output_handler') . "\n";

root@# ./myscript.php
output_handler => ob_gzhandler

Apparently (acording to Richard Lynch):

> The ob_start() has already kicked in by this point.
> ob_flush() until there are no more buffers. 31-Mar-2006 01:36
set PHP_INI_PERDIR settings in a .htaccess file with 'php_flag' like this:

php_flag register_globals off
php_flag magic_quotes_gpc on
Ron Ludwig 10-Jan-2006 11:30
When your ISP does not allow you to add the default include directories - it might be useful to extend the 'include_path' variable:

<?php ini_set('include_path',ini_get('include_path').':../includes:');  ?>
brainiac5 dot php at aimail dot de 05-Sep-2004 07:54
To find the apache php settings try something like this.
> cd /etc/apache2
> grep -r -n -i  safe_mode_exec_dir *.conf
> grep -r -n -i safe_mode.*On *.conf

If you find a gererated file, obviously you need to find the source template for it, to change what's needed there.

I just wasted a sunny Sunday on searching for where the heck safe_mode_exec_dir was changed.

And yes, Local Value in phpinfo does mean 'changed between the php.ini file and here', as you would think.

If you have an automated virtual host configuration, such as confixx, php ini values can be spread across very many files.

They can be changed in apache config files, that can have any name, but usually will end on .conf, besides in .htaccess files.
klw at gmx dot at 05-Sep-2004 06:49
To change settings from .htaccess files, it is also required that the directory permissions configured in Apache allow this.

The <Directory /foo/bar> entry in httpd.conf MUST contain "AllowOverride All" or at least "AllowOverride Options" to read PHP settings from the .htaccess file.

E.g. in Fedora Core 2, the default settings for /var/www/html/ are "AllowOverride None", so changing PHP settings via .htaccess for applications installed below /var/www/html/ will not work.
sean at php dot net 13-Aug-2004 06:54
While this doesn't belong in the manual, it should be useful for people looking on this page for zend_optimizer.* ini options, which are commonly installed:

Information on the "zend_optimizer.optimization_level" and "zend_optimizer.enable_loader" options is available at:
davey at its-explosive dot net 17-Mar-2003 06:42
If you set something using php_admin_value in httpd.conf it is then not possible to be set the value at runtime, even if it's NOT PHP_INI_SYSTEM.

Just an interesting note for Server admins this might come in handy to disable setting of certain things... like allow_url_fopen.

- Davey
miroslav AT simunic DOT de 29-Sep-2002 08:26
If it's not your server and therefore you want to hide the data in your session variables from other users, it?s very useful to set the session.save_handler in your scripts to shared memory with:

<?php ini_set('session.save_handler','mm'); ?>

Remember: You have to set it in every script that uses the session variables BEFORE "session_start()" or php won't find them.
Tr909 at com dot nospam dot bigfoot 12-Jun-2002 10:04
[[[Editors note: Yes, this is very true.  Same with
register_globals, magic_quotes_gpc and others.

Many settings, although they do get set, have no influence in your script.... like upload_max_filesize will get set but uploaded files are already passed to your PHP script before the settings are changed.

Also other settings, set by ini_set(), may be to late because of this (post_max_size etc.).
beware, try settings thru php.ini or .htaccess.
johnzoet at netscape dot com 13-Mar-2002 06:13
[[[Editors note: Just because you're able to set something
doesn't mean it will work as expected.  Depends on the
setting.  For example. setting register_globals at
runtime will be of little use as its job has already
been completed by the time it reaches your script.

When a setting can not be changed in a user script, the return value of ini_set is "empty", not "false" as you may expect.
If you check in your script for return value is "false" the script will continue processing, although the setting has not been set.
The boolean return value is used for settings that can be changed in a script. Otherwise the empty value is returned.
To test for both error conditions use:

if (empty($blnResult) or (!$blnResult)) {
"setting cannot be set";