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

Table H-3. Httpd Options

NameDefaultChangeableChangelog
async_send"0"PHP_INI_ALL 

Language Options

Table H-4. Language and Misc Configuration Options

NameDefaultChangeableChangelog
short_open_tag"1"PHP_INI_PERDIRPHP_INI_ALL in PHP <= 4.0.0.
asp_tags"0"PHP_INI_PERDIRPHP_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_PERDIRPHP_INI_ALL in PHP <= 4.0.0.
expose_php"1"php.ini only 
zend.ze1_compatibility_mode"0"PHP_INI_ALLAvailable 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

Table H-5. Resource Limits

NameDefaultChangeableChangelog
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

Table H-6. Performance Tuning

NameDefaultChangeableChangelog
realpath_cache_size"16K"PHP_INI_SYSTEMAvailable since PHP 5.1.0.
realpath_cache_ttl"120"PHP_INI_SYSTEMAvailable 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

Table H-7. Data Handling Configuration Options

NameDefaultChangeableChangelog
track_vars"On"PHP_INI_?? 
arg_separator.output"&"PHP_INI_ALLAvailable since PHP 4.0.5.
arg_separator.input"&"PHP_INI_PERDIRAvailable since PHP 4.0.5.
variables_order"EGPCS"PHP_INI_PERDIRPHP_INI_ALL in PHP <= 5.0.5.
auto_globals_jit"1"PHP_INI_PERDIRAvailable since PHP 5.0.0.
register_globals"0"PHP_INI_PERDIRPHP_INI_ALL in PHP <= 4.2.3.
register_argc_argv"1"PHP_INI_PERDIRPHP_INI_ALL in PHP <= 4.2.3.
register_long_arrays"1"PHP_INI_PERDIRAvailable since PHP 5.0.0.
post_max_size"8M"PHP_INI_PERDIRPHP_INI_SYSTEM in PHP <= 4.2.3. Available since PHP 4.0.3.
gpc_order"GPC"PHP_INI_ALL 
auto_prepend_fileNULLPHP_INI_PERDIRPHP_INI_ALL in PHP <= 4.2.3.
auto_append_fileNULLPHP_INI_PERDIRPHP_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_PERDIRPHP_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), 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.

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.

This directive was removed in PHP 6.0.0.

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 include() 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 include() 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

Table H-8. Paths and Directories Configuration Options

NameDefaultChangeableChangelog
include_path".;/path/to/php/pear"PHP_INI_ALL 
doc_rootNULLPHP_INI_SYSTEM 
user_dirNULLPHP_INI_SYSTEM 
extension_dir"/path/to/php"PHP_INI_SYSTEM 
extensionNULLphp.ini only 
cgi.check_shebang_line"1"PHP_INI_SYSTEMAvailable since PHP 5.2.0.
cgi.fix_pathinfo"1"PHP_INI_ALLAvailable since PHP 4.3.0.
cgi.force_redirect"1"PHP_INI_ALLAvailable since PHP 4.2.0.
cgi.redirect_status_envNULLPHP_INI_ALLAvailable since PHP 4.2.0.
fastcgi.impersonate"0"PHP_INI_ALLAvailable since PHP 4.3.0.
cgi.rfc2616_headers"0"PHP_INI_ALLAvailable 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 H-1. Unix include_path

include_path=".:/php/includes"

Example H-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

Table H-9. File Uploads Configuration Options

NameDefaultChangeableChangelog
file_uploads"1"PHP_INI_SYSTEMPHP_INI_ALL in PHP <= 4.2.3. Available since PHP 4.0.3.
upload_tmp_dirNULLPHP_INI_SYSTEM 
upload_max_filesize"2M"PHP_INI_PERDIRPHP_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

Table H-10. General SQL Configuration Options

NameDefaultChangeableChangelog
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 Appendix F.

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.