Language Options

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 ?>).

Note:

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 certain functions to be disabled. It takes a comma-delimited list of function names. As of PHP 8.0.0, disabling a function removes its definition, allowing userland to redefine it. Prior to PHP 8.0.0, disabling a function just prevented the function from being invoked.

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.

Warning

This directive can be circumvented and should not be considered a sufficient security measure for shared hosting environments.

disable_classes string

This directive allows certain classes to be disabled. It takes a comma-delimited list of class names. Disabling a class just prevents the class's instantiation.

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.

Warning

This directive can be circumvented and should not be considered a sufficient security measure for shared hosting environments.

Warning

This feature has been REMOVED as of PHP 8.5.0.

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).

Note:

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

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.

As of PHP 8.5.12, 8.4.27, 8.3.36 and 8.2.35, this is a soft limit: an allocation that crosses it is, in most cases, allowed to complete before the fatal error is raised, so the memory usage of a process may briefly exceed memory_limit. A separate hard limit, controlled by memory_hard_limit_percent, bounds how far it may be exceeded.

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

max_memory_limit int

Available as of PHP 8.5.0. This startup-only setting controls the maximum value that memory_limit may be configured to, either at startup or at runtime (e.g. via ini_set()). Setting memory_limit to a value exceeding max_memory_limit results in a warning and the value being capped. Set to -1 (the default) to impose no upper bound.

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

memory_hard_limit_percent int

Available as of PHP 8.5.12, 8.4.27, 8.3.36 and 8.2.35. Sets a hard memory limit, expressed as a percentage of memory_limit. For example, with memory_limit=128M and memory_hard_limit_percent=150, the hard limit is 192M. Unlike memory_limit, the hard limit can never be exceeded.

Warning

This directive was introduced in the security releases of 21 October 2026, which fix two critical vulnerabilities (CVE-2026-109618, CVE-2026-109619) that can allow unauthenticated remote code execution, one of them triggered through out-of-memory handling. If this directive is not recognized, the PHP version in use is affected by these vulnerabilities and must be updated immediately. See the » security advisory for details.

When an allocation exceeds memory_limit (the soft limit), the memory is still allocated, and the usual fatal error is raised once the engine reaches a safe point. Shutdown functions registered with register_shutdown_function() still run.

When an allocation would exceed the hard limit, the process is terminated immediately with exit status 137. A message is written directly to the standard error stream, looking something like this:

Hard memory limit of 201326592 bytes exhausted

The message does not go through the error handling mechanism, so it is not passed to error handlers or written to the error_log. No further PHP code runs: shutdown functions, destructors and output buffer handlers are all skipped.

The value must be 100 or greater, or -1.

When unset (the default) or set to -1, the hard limit is twice memory_limit if memory_limit is 1G or less, and memory_limit plus 1G otherwise. For example, with the default memory_limit=128M, the hard limit is 256M, and with memory_limit=4G it is 5G. If memory_limit is set to -1, there is no hard limit either.

Caution

A value of 100 makes the hard limit equal to memory_limit, which turns most out-of-memory conditions into an immediate termination of the process instead of a fatal error. Shutdown-time work such as logging, releasing locks or finishing a response will then never run on out-of-memory.

Note:

Because the process exits without producing output, in multi-request environments such as PHP-FPM the worker serving the request is terminated and the client receives no response from PHP; the process manager starts a replacement worker. Exit status 137 is also the status reported for a process killed by SIGKILL, for example by the kernel OOM killer or a container runtime, so check the standard error stream to tell the cases apart.

See also: max_execution_time.

Performance Tuning

Note:

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

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.

Note:

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.

Warning

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.

Note:

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.

Warning

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.

Warning

This feature has been DEPRECATED as of PHP 8.5.0. Relying on this feature is highly discouraged.

Note:

Deriving $_SERVER['argc'] and $_SERVER['argv'] from the query string for non-CLI SAPIs has been deprecated. Configure register_argc_argv=0 and switch to either $_GET or $_SERVER['QUERY_STRING'] to access the information, after verifying that the usage is safe.

enable_post_data_reading bool

Disabling this option causes $_POST and $_FILES not to be populated. The request body remains unconsumed in php://input and can be read manually or parsed via request_parse_body(). 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.

Note:

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

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

include_path=".:/php/includes"

Example #2 Windows include_path

include_path=".;c:\php\includes"

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.

Note:

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.

Note:

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.

As of PHP 8.3.0, open_basedir no longer accepts a paths containing the parent directory (..) when set at runtime using ini_set().

Note:

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

Warning

open_basedir does not restrict access to Unix domain sockets. PHP socket functions such as stream_socket_client() and fsockopen() can connect to a Unix socket path (e.g. unix:///var/run/docker.sock) regardless of the open_basedir setting.

Caution

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.

Note:

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.

Note:

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

cgi.rfc2616_headers bool

Tells PHP what type of headers to use when sending HTTP response code. If it is disabled, PHP sends a » RFC 3875 "Status:" header that is supported by Apache and other web servers. When this option is enabled, 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 disabled unless you know what you're doing.

fastcgi.impersonate bool

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). Enable if running under IIS. Default is disabled.

fastcgi.logging bool

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

File Uploads

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

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.

Warning

This feature has been REMOVED as of PHP 7.2.0.

Windows Specific

Here's a short explanation of the configuration directives.

windows.show_crt_warning bool

This directive shows the Windows CRT warnings when enabled.