CascadiaPHP 2024

Description of core php.ini directives

This list includes the core php.ini directives you can set to configure your PHP setup. Directives handled by extensions are listed and detailed at the extension documentation pages respectively; Information on the session directives for example can be found at the sessions page.


The defaults listed here are used when php.ini is not loaded; the values for the production and development php.ini may vary.

Language Options

Language and Misc Configuration Options
Name Default Changeable Changelog
short_open_tag "1" INI_PERDIR  
precision "14" INI_ALL  
serialize_precision "-1" INI_ALL Prior to PHP 7.1.0, the default value was 17.
disable_functions "" INI_SYSTEM only  
disable_classes "" php.ini only  
exit_on_timeout "" INI_ALL  
expose_php "1" php.ini only  
hard_timeout "2" INI_SYSTEM Available as of PHP 7.1.0.
zend.exception_ignore_args "0" INI_ALL Available as of PHP 7.4.0
zend.multibyte "0" INI_ALL  
zend.script_encoding NULL INI_ALL  
zend.detect_unicode NULL INI_ALL  
zend.signal_check "0" INI_SYSTEM  
zend.assertions "1" INI_ALL with restrictions  
zend.exception_string_param_max_len "15" INI_ALL Available as of PHP 8.0.0.

Here's a short explanation of the configuration directives.

short_open_tag bool

Tells PHP whether the short form (<? ?>) of PHP's open tag should be allowed. If you want to use PHP in combination with XML, you can disable this option in order to use <?xml ?> inline. Otherwise, you can print it with PHP, for example: <?php echo '<?xml version="1.0"?>'; ?>. Also, if disabled, you must use the long form of the PHP open tag (<?php ?>).


This directive does not affect the shorthand <?=, which is always available.

precision int
The number of significant digits displayed in floating point numbers. -1 means that an enhanced algorithm for rounding such numbers will be used.
serialize_precision int
The number of significant digits stored while serializing floating point numbers. -1 means that an enhanced algorithm for rounding such numbers will be used.
expose_php bool

Exposes to the world that PHP is installed on the server, which includes the PHP version within the HTTP header (e.g., X-Powered-By: PHP/5.3.7).

disable_functions string
This directive allows disables certain functions. It takes on a comma-delimited list of function names. As of PHP 8.0.0, disabling a function removes it definition allowing userland to redefine it. Prior to PHP 8.0.0, disabling a function just prevent invoking the function. Only internal functions can be disabled using this directive. User-defined functions are unaffected. This directive must be set in php.ini. It cannot be set in httpd.conf.
disable_classes string

This directive allows disables certain classes. It takes on a comma-delimited list of class names. Disabling a class just prevent instantiating the class.

Only internal classes can be disabled using this directive. User-defined classes are unaffected.

This directive must be set in php.ini. It cannot be set in httpd.conf.
zend.assertions int
When set to 1, assertion code will be generated and executed (development mode). When set to 0, assertion code will be generated but it will be skipped (not executed) at runtime. When set to -1, assertion code will not be generated, making the assertions zero-cost (production mode).


If a process is started in production mode, zend.assertions cannot be changed at runtime, since the code for assertions was not generated.

If a process is started in development mode, zend.assertions cannot be set to -1 at runtime.

zend.exception_string_param_max_len int
The maximum length of string function arguments in stringified stack traces. Must range between "0" and "1000000".
hard_timeout int

When the timeout set in max_execution_time has been hit, the PHP runtime will tear down resources gracefully. If something gets stuck while this happens, the hard timeout will tick for the set amount of seconds. When the hard timeout is hit, PHP will exit ungracefully. When set to 0, the hard timeout will never activate.

When PHP stops from a hard timeout, it will look something like this:

Fatal error: Maximum execution time of 30+2 seconds exceeded (terminated) in Unknown on line 0

zend.exception_ignore_args bool

Excludes arguments from stack traces generated from exceptions.

zend.multibyte bool

Enables parsing of source files in multibyte encodings. Enabling zend.multibyte is required to use character encodings like SJIS, BIG5, etc that contain special characters in multibyte string data. ISO-8859-1 compatible encodings like UTF-8, EUC, etc do not require this option.

Enabling zend.multibyte requires the mbstring extension to be available.

zend.script_encoding string

This value will be used unless a declare(encoding=...) directive appears at the top of the script. When ISO-8859-1 incompatible encoding is used, both zend.multibyte and zend.script_encoding must be used.

Literal strings will be transliterated from zend.script_encoding to mbstring.internal_encoding, as if mb_convert_encoding() would have been called.

zend.detect_unicode bool

Check for BOM (Byte Order Mark) and see if the file contains valid multibyte characters. This detection is performed before processing of __halt_compiler(). Available only in Zend Multibyte mode.

zend.signal_check bool

To check for replaced signal handlers on shutdown.

exit_on_timeout bool

This is an Apache1 mod_php-only directive that forces an Apache child to exit if a PHP execution timeout occurred. Such a timeout causes an internal longjmp() call in Apache1 which can leave some extensions in an inconsistent state. By terminating the process any outstanding locks or memory will be cleaned up.

Resource Limits

Resource Limits
Name Default Changeable Changelog
memory_limit "128M" INI_ALL  

Here's a short explanation of the configuration directives.

memory_limit int

This sets the maximum amount of memory in bytes that a script is allowed to allocate. This helps prevent poorly written scripts for eating up all available memory on a server. Note that to have no memory limit, set this directive to -1.

When an int is used, the value is measured in bytes. Shorthand notation, as described in this FAQ, may also be used.

See also: max_execution_time.

Performance Tuning

Performance Tuning
Name Default Changeable Changelog
realpath_cache_size "4M" INI_SYSTEM Prior to PHP 7.0.16 and 7.1.2, the default was "16K"
realpath_cache_ttl "120" INI_SYSTEM  


Using open_basedir will disable the realpath cache.

Here's a short explanation of the configuration directives.

realpath_cache_size int

Determines the size of the realpath cache to be used by PHP. This value should be increased on systems where PHP opens many files, to reflect the quantity of the file operations performed.

The size represents the total number of bytes in the path strings stored, plus the size of the data associated with the cache entry. This means that in order to store longer paths in the cache, the cache size must be larger. This value does not directly control the number of distinct paths that can be cached.

The size required for the cache entry data is system dependent.

realpath_cache_ttl int

Duration of time (in seconds) for which to cache realpath information for a given file or directory. For systems with rarely changing files, consider increasing the value.

Data Handling

Data Handling Configuration Options
Name Default Changeable Changelog
arg_separator.output "&" INI_ALL  
arg_separator.input "&" INI_PERDIR  
variables_order "EGPCS" INI_PERDIR  
request_order "" INI_PERDIR  
auto_globals_jit "1" INI_PERDIR  
register_argc_argv "1" INI_PERDIR  
enable_post_data_reading "1" INI_PERDIR  
post_max_size "8M" INI_PERDIR  
auto_prepend_file NULL INI_PERDIR  
auto_append_file NULL INI_PERDIR  
default_mimetype "text/html" INI_ALL  
default_charset "UTF-8" INI_ALL  
input_encoding "" INI_ALL  
output_encoding "" INI_ALL  
internal_encoding "" INI_ALL  

Here's a short explanation of the configuration directives.

arg_separator.output string

The separator used in PHP generated URLs to separate arguments.

arg_separator.input string

List of separator(s) used by PHP to parse input URLs into variables.


Every character in this directive is considered as separator!

variables_order string

Sets the order of the EGPCS (Environment, Get, Post, Cookie, and Server) variable parsing. For example, if variables_order is set to "SP" then PHP will create the superglobals $_SERVER and $_POST, but not create $_ENV, $_GET, and $_COOKIE. Setting to "" means no superglobals will be set.


In both the CGI and FastCGI SAPIs, $_SERVER is also populated by values from the environment; S is always equivalent to ES regardless of the placement of E elsewhere in this directive.


The content and order of $_REQUEST is also affected by this directive.

request_order string

This directive describes the order in which PHP registers GET, POST and Cookie variables into the _REQUEST array. Registration is done from left to right, newer values override older values.

If this directive is not set, variables_order is used for $_REQUEST contents.

Note that the default distribution php.ini files does not contain the 'C' for cookies, due to security concerns.

auto_globals_jit bool

When enabled, the SERVER, REQUEST, and ENV variables are created when they're first used (Just In Time) instead of when the script starts. If these variables are not used within a script, having this directive on will result in a performance gain.


Usage of SERVER, REQUEST, and ENV variables is checked during the compile time so using them through e.g. variable variables will not cause their initialization.

register_argc_argv bool
Tells PHP whether to declare the argv & argc variables (that would contain the GET information). See also command line.
enable_post_data_reading bool
Disabling this option causes $_POST and $_FILES not to be populated. The only way to read postdata will then be through the php://input stream wrapper. This can be useful to proxy requests or to process the POST data in a memory efficient fashion.
post_max_size int
Sets max size of post data allowed. This setting also affects file upload. To upload large files, this value must be larger than upload_max_filesize. Generally speaking, memory_limit should be larger than post_max_size. When an int is used, the value is measured in bytes. Shorthand notation, as described in this FAQ, may also be used. If the size of post data is greater than post_max_size, the $_POST and $_FILES superglobals are empty. This can be tracked in various ways, e.g. by passing the $_GET variable to the script processing the data, i.e. <form action="edit.php?processed=1">, and then checking if $_GET['processed'] is set.


PHP allows shortcuts for byte values, including K (kilo), M (mega) and G (giga). PHP will do the conversions automatically if you use any of these. Be careful not to exceed the 32 bit signed integer limit (if you're using 32bit versions) as it will cause your script to fail.

Changelog for post_max_size
Version Description
5.3.4 post_max_size = 0 will not disable the limit when the content type is application/x-www-form-urlencoded or is not registered with PHP.
5.3.2 , 5.2.12 Allow unlimited post size by setting post_max_size to 0.

auto_prepend_file string

Specifies the name of a file that is automatically parsed before the main file. The file is included as if it was called with the require function, so include_path is used.

The special value none disables auto-prepending.

auto_append_file string

Specifies the name of a file that is automatically parsed after the main file. The file is included as if it was called with the require function, so include_path is used.

The special value none disables auto-appending.

Note: If the script is terminated with exit(), auto-append will not occur.

default_mimetype string

By default, PHP will output a media type using the Content-Type header. To disable this, simply set it to be empty.

PHP's built-in default media type is set to text/html.

default_charset string

"UTF-8" is the default value and its value is used as the default character encoding for htmlentities(), html_entity_decode() and htmlspecialchars() if the encoding parameter is omitted. The value of default_charset will also be used to set the default character set for iconv functions if the iconv.input_encoding, iconv.output_encoding and iconv.internal_encoding configuration options are unset, and for mbstring functions if the mbstring.http_input mbstring.http_output mbstring.internal_encoding configuration option is unset.

All versions of PHP will use this value as the charset within the default Content-Type header sent by PHP if the header isn't overridden by a call to header().

Setting default_charset to an empty value is not recommended.

input_encoding string

This setting is used for multibyte modules such as mbstring and iconv. Default is empty.

output_encoding string

This setting is used for multibyte modules such as mbstring and iconv. Default is empty.

internal_encoding string

This setting is used for multibyte modules such as mbstring and iconv. Default is empty. If empty, default_charset is used.

Paths and Directories

Paths and Directories Configuration Options
Name Default Changeable Changelog
include_path ".;/path/to/php/pear" INI_ALL  
open_basedir NULL INI_ALL  
doc_root NULL INI_SYSTEM  
user_dir NULL INI_SYSTEM  
user_ini.cache_ttl "300" INI_SYSTEM  
user_ini.filename ".user.ini" INI_SYSTEM  
extension_dir "/path/to/php" INI_SYSTEM  
extension NULL php.ini only  
zend_extension NULL php.ini only  
cgi.check_shebang_line "1" INI_SYSTEM  
cgi.discard_path "0" INI_SYSTEM  
cgi.fix_pathinfo "1" INI_SYSTEM  
cgi.force_redirect "1" INI_SYSTEM  
cgi.nph "0" INI_SYSTEM  
cgi.redirect_status_env NULL INI_SYSTEM  
cgi.rfc2616_headers "0" INI_ALL  
fastcgi.impersonate "0" INI_SYSTEM  
fastcgi.logging "1" INI_SYSTEM  

Here's a short explanation of the configuration directives.

include_path string

Specifies a list of directories where the require, include, fopen(), file(), readfile() and file_get_contents() functions look for files. The format is like the system's PATH environment variable: a list of directories separated with a colon in Unix or semicolon in Windows.

PHP considers each entry in the include path separately when looking for files to include. It will check the first path, and if it doesn't find it, check the next path, until it either locates the included file or returns with an E_WARNING or an E_ERROR. You may modify or set your include path at runtime using set_include_path().

Example #1 Unix include_path


Example #2 Windows include_path


Using a . in the include path allows for relative includes as it means the current directory. However, it is more efficient to explicitly use include './file' than having PHP always check the current directory for every include.


ENV variables are also accessible in .ini files. As such it is possible to reference the home directory using ${LOGIN} and ${USER}.

Environment variables may vary between Server APIs as those environments may be different.

Example #3 Unix include_path using ${USER} env variable

include_path = ".:${USER}/pear/php"

open_basedir string

Limit the files that can be accessed by PHP to the specified directory-tree, including the file itself.

When a script tries to access the filesystem, for example using include, or fopen(), the location of the file is checked. When the file is outside the specified directory-tree, PHP will refuse to access it. All symbolic links are resolved, so it's not possible to avoid this restriction with a symlink. If the file doesn't exist then the symlink couldn't be resolved and the filename is compared to (a resolved) open_basedir.

open_basedir can affect more than just filesystem functions; for example if MySQL is configured to use mysqlnd drivers, LOAD DATA INFILE will be affected by open_basedir. Much of the extended functionality of PHP uses open_basedir in this way.

The special value . indicates that the working directory of the script will be used as the base-directory. This is, however, a little dangerous as the working directory of the script can easily be changed with chdir().

In httpd.conf, open_basedir can be turned off (e.g. for some virtual hosts) the same way as any other configuration directive with "php_admin_value open_basedir none".

Under Windows, separate the directories with a semicolon. On all other systems, separate the directories with a colon. As an Apache module, open_basedir paths from parent directories are now automatically inherited.

The restriction specified with open_basedir is a directory name, not a prefix.

The default is to allow all files to be opened.


open_basedir can be tightened at run-time. This means that if open_basedir is set to /www/ in php.ini a script can tighten the configuration to /www/tmp/ at run-time with ini_set(). When listing several directories, you can use the PATH_SEPARATOR constant as a separator regardless of the operating system.


Using open_basedir will set realpath_cache_size to 0 and thus disable the realpath cache.


open_basedir is just an extra safety net, that is in no way comprehensive, and can therefore not be relied upon when security is needed.

doc_root string

PHP's "root directory" on the server. Only used if non-empty. If PHP was not compiled with FORCE_REDIRECT, you should set doc_root if you are running PHP as a CGI under any web server (other than IIS). The alternative is to use the cgi.force_redirect configuration below.

user_ini.cache_ttl int

user_ini.filename string

user_dir string

The base name of the directory used on a user's home directory for PHP files, for example public_html .

extension_dir string

In what directory PHP should look for dynamically loadable extensions. It is recommended to specify an absolute path. See also: enable_dl, and dl().

extension string

Which dynamically loadable extensions to load when PHP starts up.

zend_extension string

Name of dynamically loadable Zend extension (for example XDebug) to load when PHP starts up.

cgi.check_shebang_line bool

Controls whether CGI PHP checks for line starting with #! (shebang) at the top of the running script. This line might be needed if the script support running both as stand-alone script and via PHP CGI. PHP in CGI mode skips this line and ignores its content if this directive is turned on.

cgi.discard_path bool

If this is enabled, the PHP CGI binary can safely be placed outside of the web tree and people will not be able to circumvent .htaccess security.

cgi.fix_pathinfo bool

Provides real PATH_INFO/ PATH_TRANSLATED support for CGI. PHP's previous behaviour was to set PATH_TRANSLATED to SCRIPT_FILENAME, and to not grok what PATH_INFO is. For more information on PATH_INFO, see the CGI specs. Setting this to 1 will cause PHP CGI to fix its paths to conform to the spec. A setting of zero causes PHP to behave as before. It is turned on by default. You should fix your scripts to use SCRIPT_FILENAME rather than PATH_TRANSLATED.

cgi.force_redirect bool

cgi.force_redirect is necessary to provide security running PHP as a CGI under most web servers. Left undefined, PHP turns this on by default. You can turn it off at your own risk.


Windows Users: When using IIS this option must be turned off. For OmniHTTPD or Xitami the same applies.

cgi.nph bool

If cgi.nph is enabled it will force cgi to always sent Status: 200 with every request.

cgi.redirect_status_env string

If cgi.force_redirect is turned on, and you are not running under Apache or Netscape (iPlanet) web servers, you may need to set an environment variable name that PHP will look for to know it is OK to continue execution.


Setting this variable may cause security issues, know what you are doing first.

cgi.rfc2616_headers int

Tells PHP what type of headers to use when sending HTTP response code. If it's set to 0, PHP sends a » RFC 3875 "Status:" header that is supported by Apache and other web servers. When this option is set to 1, PHP will send » RFC 2616 compliant headers.

If this option is enabled, and you are running PHP in a CGI environment (e.g. PHP-FPM) you should not use standard RFC 2616 style HTTP status response headers, you should instead use their RFC 3875 equivalent e.g. instead of header("HTTP/1.0 404 Not found"); you should use header("Status: 404 Not Found");

Leave it set to 0 unless you know what you're doing.

fastcgi.impersonate string

FastCGI under IIS (on WINNT based OS) supports the ability to impersonate security tokens of the calling client. This allows IIS to define the security context that the request runs under. mod_fastcgi under Apache does not currently support this feature (03/17/2002) Set to 1 if running under IIS. Default is zero.

fastcgi.logging bool

Turns on SAPI logging when using FastCGI. Default is to enable logging.

File Uploads

File Uploads Configuration Options
Name Default Changeable Changelog
file_uploads "1" INI_SYSTEM  
upload_tmp_dir NULL INI_SYSTEM  
max_input_nesting_level 64 INI_PERDIR  
max_input_vars 1000 INI_PERDIR  
upload_max_filesize "2M" INI_PERDIR  
max_file_uploads 20 INI_PERDIR  

Here's a short explanation of the configuration directives.

file_uploads bool

Whether or not to allow HTTP file uploads. See also the upload_max_filesize, upload_tmp_dir, and post_max_size directives.

upload_tmp_dir string

The temporary directory used for storing files when doing file upload. Must be writable by whatever user PHP is running as. If not specified PHP will use the system's default.

If the directory specified here is not writable, PHP falls back to the system default temporary directory. If open_basedir is on, then the system default directory must be allowed for an upload to succeed.

upload_max_filesize int

The maximum size of an uploaded file.

post_max_size must be larger than this value.

When an int is used, the value is measured in bytes. Shorthand notation, as described in this FAQ, may also be used.
max_file_uploads int

The maximum number of files allowed to be uploaded simultaneously. Upload fields left blank on submission do not count towards this limit.

General SQL

General SQL Configuration Options
Name Default Changeable Changelog
sql.safe_mode "0" INI_SYSTEM Removed as of PHP 7.2.0

Here's a short explanation of the configuration directives.

sql.safe_mode bool

If turned on, database connection functions that specify default values will use those values in place of any user-supplied arguments. For details on the default values, see the documentation for the relevant connection functions.


This feature has been REMOVED as of PHP 7.2.0.

Windows Specific

Windows Specific Configuration Options
Name Default Changeable Changelog
windows.show_crt_warning "0" INI_ALL  

Here's a short explanation of the configuration directives.

windows.show_crt_warning bool

This directive shows the Windows CRT warnings when enabled.

add a note

User Contributed Notes 9 notes

4 years ago explains the memory_limit setting nicely.
Simone Pellegatta
3 years ago
Be careful while using auto_prepend_file.

When the custom exception handler, set by set_exception_handler(), handles an uncaught exception, it interrupts the execution of every script.

If the script with the unhandled exception has been automatically prepended or included by an automatically prepended script, however, the main script will continue running anyway.

This could cause several issues: when we think that throwing an exception would automatically interrupt the current application, a whole chunk of code is going to run anyway.
diamondeagle at webmail dot co dot za
4 years ago
Note regarding the upload_tmp_dir setting and UNC Paths:

When using PHP on Windows OS and IIS FastCGI, if you need to use a UNC path to a folder on a network drive for the upload_tmp_dir setting then you must use three \ characters at the front of the UNC path.

Windows and PHP use the first slash as an escape character, so if you only use two slashes then it passes a UNC path with just one backslash. That is not valid for UNC paths and you many experience problems when uploading files, such as errors saying that "PHP is missing a temporary folder".

upload_tmp_dir = "\\\path\to\your\folder"

upload_tmp_dir = "\\path\to\your\folder"
1 month ago
you get a misleading error if a directory doesn't exist or the user lacks permission to access it.

open_basedir restriction in effect. File(/tmp/php_session) is not within the allowed path(s): /tmp/php_session
andre dot wetter at myelco dot ch
3 years ago
If you use Microsoft IIS Windows and want to use open_basedir restrictions with multiple dirs you have to set them into single quotes in the main config xml file of IIS (C:\Windows\System32\inetsrv\config\applicationHost.config). Works fine in IIS 10.

Multiple files with single quotes and ; for windows:
"C:\php\php-cgi.exe|-d open_basedir='C:\Windows\Temp\;D:\mywebsite1\'"

Only one dir works fine without single quotes:
"C:\php\php-cgi.exe|-d open_basedir=D:\mywebsite1\"

In my main config xml file of IIS there are 2 nodes to set per website and the definitions have to be equal:
fernandobasso dot br at gmail dot com
7 years ago
This might help in case someone happens to maintain old applications with a charset other than utf-8.

According to the docs, you can override the default charset if you use `header()`.

Suppose php.ini sets the default_charset to "UTF-8", but you need a legacy charset, like ISO-8859-1.


<?php header('Content-Type: text/html; Charset=ISO-8859-1'); ?>

would not override the charset, just add it as well and the result
was a response header like (note the two charsets):

Content-Type:"text/html; Charset=ISO-8859-1;charset=UTF-8"

I found it strange the default one as `charset` with a lowercase `c`
as opposed to my custom charset with an uppercase `C`.

What solved was to _override_ the charset using all lowercase letters
as well for the word “charset”:

<?php header('content-type: text/html; charset=ISO-8859-1'); ?>

Then, the double charset from the response headers disappeared, and only the single, custom charset remained.
leo at korfu dot cz
18 years ago
"If the size of post data is greater than post_max_size..."

It seems that a more elegant way is comparison between post_max_size and $_SERVER['CONTENT_LENGTH']. Please note that the latter includes not only size of uploaded file plus post data but also multipart sequences. Leo
dougal at gunters dot org
8 years ago
It appears that if you use both the 'include_path' directives and 'open_basedir', that file searches will hit the include path *first*, before local files. But if 'open_basedir' is not in use, then local files are found first. For example, suppose you have code in '/var/www/myfile.php' which does:


Further, assume that there is a local file '/var/www/config.php', and there is also a file '/var/local/php/config.php'.

Next, if your php.ini has:

include_path = /var/local/php/

Normally, this would look for '/var/www/config.php' first, and if not found, then it would try '/var/local/php/config.php'.

But if you also have this in php.ini:

open_basedir = /var/www/:/var/local/php/

Then the require would reverse the order of the search, and load '/var/local/php/config.php', even when the local 'config.php' file exists.

Furthermore, if include_path contains directories not in open_basedir, you can end up with a fatal error. For example, change the directive to:

open_basedir = /var/www/:/var/local/includes/php/

Now the require will first find '/var/local/php/config.php' from the include_path, try to include it, but be unable to because of the open_basedir restrictions.
Anton Bannikov
4 years ago
I had a problem with 'open_basedir =' string in php.ini. This string was writtren in VirtualHost Directory directive of Apache2 and successfully rewrote the same php.ini setting! It happened with VestaCP, but I think, it's a common way. Goog luck!
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