## 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.

## Httpd Options

Httpd Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
async_send | "0" | PHP_INI_ALL |

## Language Options

Language and Misc Configuration Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
short_open_tag | "1" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.0.0.
asp_tags | "0" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.0.0.
precision | "14" | PHP_INI_ALL |
y2k_compliance | "1" | PHP_INI_ALL |
allow_call_time_pass_reference | "1" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.0.0.
expose_php | "1" | php.ini only |
zend.ze1_compatibility_mode | "0" | PHP_INI_ALL | Available since PHP 5.0.0.

Here's a short explanation of the configuration directives.

`short_open_tag` boolean

  Tells 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 also affects the shorthand `<?=` , which is identical to `<? echo` . Use of this shortcut requires `short_open_tag` to be on.

`asp_tags` boolean
  Enables the use of ASP-like <% %> tags in addition to the usual <?php ?> tags. This includes the variable-value printing shorthand of <%= $value %>. For more information, see Escaping from HTML.

  > Note: Support for ASP-style tags was added in 3.0.4.

`precision` integer
  The number of significant digits displayed in floating point numbers.
`y2k_compliance` boolean
  Enforce year 2000 compliance (will cause problems with non-compliant browsers)
`allow_call_time_pass_reference` boolean

  Whether to warn when arguments are passed by reference at function call time. This method is deprecated and is likely to be unsupported in future versions of PHP/Zend. The encouraged method of specifying which arguments should be passed by reference is in the function declaration. You're encouraged to try and turn this option Off and make sure your scripts work properly with it in order to ensure they will work with future versions of the language (you will receive a warning each time you use this feature).

  Passing arguments by reference at function call time was deprecated for code cleanliness reason. Function can modify its argument in undocumented way if it didn't declared that the argument is passed by reference. To prevent side-effects it's better to specify which arguments are passed by reference in function declaration only.

  See also References Explained.

`expose_php` boolean

  Decides whether PHP may expose the fact that it is installed on the server (e.g. by adding its signature to the Web server header). It is no security threat in any way, but it makes it possible to determine whether you use PHP on your server or not.

`zend.ze1_compatibility_mode` boolean

  Enable compatibility mode with Zend Engine 1 (PHP 4). It affects the cloning, casting (objects with no properties cast to `FALSE` or 0), and comparing of objects. In this mode, objects are passed by value instead of reference by default.

  See also the section titled Migrating from PHP 4 to PHP 5.

## Resource Limits

Resource Limits
Name | Default | Changeable | Changelog
--- | --- | --- | ---
memory_limit | "128M" | PHP_INI_ALL | "8M" before PHP 5.2.0, "16M" in PHP 5.2.0

Here's a short explanation of the configuration directives.

`memory_limit` integer

  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.

  Prior to PHP 5.2.1, in order to use this directive it had to be enabled at compile time by using -enable-memory-limit in the configure line. This was also required to define the functions memory_get_usage() and memory_get_peak_usage().

  When an integer is used, the value is measured in bytes. You may also use shorthand notation as described in this FAQ.

See also: max_execution_time.

## Performance Tuning

Performance Tuning
Name | Default | Changeable | Changelog
--- | --- | --- | ---
realpath_cache_size | "16K" | PHP_INI_SYSTEM | Available since PHP 5.1.0.
realpath_cache_ttl | "120" | PHP_INI_SYSTEM | Available since PHP 5.1.0.

Here's a short explanation of the configuration directives.

`realpath_cache_size` integer

  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.

`realpath_cache_ttl` integer

  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
--- | --- | --- | ---
track_vars | "On" | PHP_INI_?? |
arg_separator.output | "&" | PHP_INI_ALL | Available since PHP 4.0.5.
arg_separator.input | "&" | PHP_INI_PERDIR | Available since PHP 4.0.5.
variables_order | "EGPCS" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 5.0.5.
auto_globals_jit | "1" | PHP_INI_PERDIR | Available since PHP 5.0.0.
register_globals | "0" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3.
register_argc_argv | "1" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3.
register_long_arrays | "1" | PHP_INI_PERDIR | Available since PHP 5.0.0.
post_max_size | "8M" | PHP_INI_PERDIR | PHP_INI_SYSTEM in PHP <= 4.2.3. Available since PHP 4.0.3.
gpc_order | "GPC" | PHP_INI_ALL |
auto_prepend_file | NULL | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3.
auto_append_file | NULL | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3.
default_mimetype | "text/html" | PHP_INI_ALL |
default_charset | "" | PHP_INI_ALL |
always_populate_raw_post_data | "0" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3. Available since PHP 4.1.0.
allow_webdav_methods | "0" | PHP_INI_PERDIR |

Here's a short explanation of the configuration directives.

`track_vars` boolean

  If enabled, then Environment, GET, POST, Cookie, and Server variables can be found in the global associative arrays $_ENV, $_GET, $_POST, $_COOKIE, and $_SERVER.

  Note that as of PHP 4.0.3, `track_vars` is always turned on.

`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.

  If the deprecated register_globals directive is on (removed as of PHP 6.0.0), then variables_order also configures the order the ENV, GET, POST, COOKIE and SERVER variables are populated in global scope. So for example if variables_order is set to "EGPCS", register_globals is enabled, and both $_GET['action'] and $_POST['action'] are set, then $action will contain the value of $_POST['action'] as P comes after G in our example directive value.

  Warning

  In both the CGI and FastCGI SAPIs, $_SERVER is also populated by values from the environment; S is always equivelant 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.

`auto_globals_jit` boolean

  When enabled, the SERVER 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.

  The PHP directives register_globals, register_long_arrays, and register_argc_argv must be disabled for this directive to have any affect. Since PHP 5.1.3 it is not necessary to have register_argc_argv disabled.

`register_globals` boolean

  Whether or not to register the EGPCS (Environment, GET, POST, Cookie, Server) variables as global variables.

  As of » PHP 4.2.0, this directive defaults to off.

  Please read the security chapter on Using register_globals for related information.

  Please note that `register_globals` cannot be set at runtime (ini_set()). Although, you can use .htaccess if your host allows it as described above. An example .htaccess entry: `php_flag register_globals off` .

  > Note: `register_globals` is affected by the variables_order directive.

  Warning

  This feature is DEPRECATED and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

`register_argc_argv` boolean
  Tells PHP whether to declare the argv & argc variables (that would contain the GET information). See also command line. Also, this directive became available in PHP 4.0.0 and was always "on" before that.
`register_long_arrays` boolean
  Tells PHP whether or not to register the deprecated long $HTTP_*_VARS type predefined variables. When On (default), long predefined PHP variables like $HTTP_GET_VARS will be defined. If you're not using them, it's recommended to turn them off, for performance reasons. Instead, use the superglobal arrays, like $_GET. This directive became available in PHP 5.0.0 and was dropped in PHP 6.0.0.
`post_max_size` integer
  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. If memory limit is enabled by your configure script, memory_limit also affects file uploading. Generally speaking, memory_limit should be larger than `post_max_size` . When an integer is used, the value is measured in bytes. You may also use shorthand notation as described in this FAQ. 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.
`gpc_order` string

  Set the order of GET/POST/COOKIE variable parsing. The default setting of this directive is "GPC". Setting this to "GP", for example, will cause PHP to completely ignore cookies and to overwrite any GET method variables with POST-method variables of the same name.

  > Note: This option is not available in PHP 4. Use variables_order instead.

`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

`default_charset` string

  As of 4.0.0, PHP always outputs a character encoding by default in the Content-type: header. To disable sending of the charset, simply set it to be empty.

`always_populate_raw_post_data` boolean

  Always populate the $HTTP_RAW_POST_DATA containing the raw POST data. Otherwise, the variable is populated only with unrecognized MIME type of the data. However, the preferred method for accessing the raw POST data is php://input. $HTTP_RAW_POST_DATA is not available with enctype="multipart/form-data".

`allow_webdav_methods` boolean

  Allow handling of WebDAV http requests within PHP scripts (eg. PROPFIND, PROPPATCH, MOVE, COPY, etc.). This directive does not exist as of PHP 4.3.2. If you want to get the post data of those requests, you have to set always_populate_raw_post_data as well.

See also: magic_quotes_gpc, magic_quotes_runtime, and magic_quotes_sybase.

## Paths and Directories

Paths and Directories Configuration Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
include_path | ".;/path/to/php/pear" | PHP_INI_ALL |
doc_root | NULL | PHP_INI_SYSTEM |
user_dir | NULL | PHP_INI_SYSTEM |
extension_dir | "/path/to/php" | PHP_INI_SYSTEM |
extension | NULL | php.ini only |
cgi.check_shebang_line | "1" | PHP_INI_SYSTEM | Available since PHP 5.2.0.
cgi.fix_pathinfo | "1" | PHP_INI_SYSTEM | Available since PHP 4.3.0. PHP_INI_ALL prior to PHP 5.2.1.
cgi.force_redirect | "1" | PHP_INI_SYSTEM | Available since PHP 4.2.0. PHP_INI_ALL prior to PHP 5.2.1.
cgi.redirect_status_env | NULL | PHP_INI_SYSTEM | Available since PHP 4.2.0. PHP_INI_ALL prior to PHP 5.2.1.
fastcgi.impersonate | "0" | PHP_INI_SYSTEM | Available since PHP 4.3.0. PHP_INI_ALL prior to PHP 5.2.1.
cgi.rfc2616_headers | "0" | PHP_INI_ALL | Available since PHP 4.3.0.

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.

  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.

`doc_root` string

  PHP's "root directory" on the server. Only used if non-empty. If PHP is configured with safe mode, no files outside this directory are served. 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_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. See also: enable_dl, and dl().

`extension` string

  Which dynamically loadable extensions to load when PHP starts up.

`cgi.check_shebang_line` boolean

  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.fix_pathinfo` boolean

  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 it's paths to conform to the spec. A setting of zero causes PHP to behave as before. Default is zero. You should fix your scripts to use SCRIPT_FILENAME rather than PATH_TRANSLATED.

`cgi.force_redirect` boolean

  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: You can safely turn this off for IIS, in fact, you must. To get OmniHTTPD or Xitami to work you must turn it off.

`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.

`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.

`cgi.rfc2616_headers` int

  Tells PHP what type of headers to use when sending HTTP response code. If it's set 0, PHP sends a 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. Leave it set to 0 unless you know what you're doing.

## File Uploads

File Uploads Configuration Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
file_uploads | "1" | PHP_INI_SYSTEM | PHP_INI_ALL in PHP <= 4.2.3. Available since PHP 4.0.3.
upload_tmp_dir | NULL | PHP_INI_SYSTEM |
upload_max_filesize | "2M" | PHP_INI_PERDIR | PHP_INI_ALL in PHP <= 4.2.3.

Here's a short explanation of the configuration directives.

`file_uploads` boolean

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

  When an integer is used, the value is measured in bytes. You may also use shorthand notation as described in this FAQ.
`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.

`upload_max_filesize` integer

  The maximum size of an uploaded file.

  When an integer is used, the value is measured in bytes. You may also use shorthand notation as described in this FAQ.

## General SQL

General SQL Configuration Options
Name | Default | Changeable | Changelog
--- | --- | --- | ---
sql.safe_mode | "0" | PHP_INI_SYSTEM |

Here's a short explanation of the configuration directives.

`sql.safe_mode` boolean

  If turned on, database connect functions that specify default values will use those values in place of supplied arguments. For default values see connect function documentation for the relevant database.

## Debugger Configuration Directives

Caution

Only PHP 3 implements a default debugger, for more information see Debugging PHP.

`debugger.host` string

  DNS name or IP address of host used by the debugger.

`debugger.port` string

  Port number used by the debugger.

`debugger.enabled` boolean

  Whether the debugger is enabled.