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PHP is a general-purpose server-side scripting language to produce dynamic web pages. It began development in 1993 and was first officially released in 1995. By the turn of the millennium, PHP began to displace Perl as the preferred "P" in the LAMP stack before being challenged in turn by Python. Even so, PHP remains a popular server-side scripting language for dynamic websites and web applications, perhaps in no small part due to the popularity of the WordPress blogging platform.


USE flags

The most important USE flags of the PHP package, the SAPI (Server API) USE flags, are apache2, cgi, and fpm. Alongside these flags, there is an elaborate list of flags to enable various features of the PHP interpreter:

USE flags for dev-lang/php The PHP language runtime engine

acl Add support for Access Control Lists
apache2 Add Apache2 support
apparmor Support FPM application confinement through sys-libs/libapparmor
argon2 Enable password hashing algorithm from app-crypt/argon2
avif Add AV1 Image Format (AVIF) support
bcmath Enable the BCMath Arbitrary Precision Mathematics extension
berkdb Add support for sys-libs/db (Berkeley DB for MySQL)
bzip2 Enable bzip2 compression support
calendar Add support for calendars (not using mcal!)
capstone Support opcache JIT disassembly through dev-libs/capstone
cdb Add support for the CDB database engine from the author of qmail
cgi Add CGI script support
cjk Add support for Multi-byte character languages (Chinese, Japanese, Korean)
cli Enable the Command-Line Interface (CLI) SAPI
coverage Include gcov symbols for test coverage and lcov reports. Only useful for extension developers, and requires GCC.
ctype Enable the Character type checking (ctype) extension
curl Add support for client-side URL transfer library
debug Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see
embed Enable embed SAPI
enchant Enable the Enchant spelling library extension using app-text/enchant
exif Add support for reading EXIF headers from JPEG and TIFF images
ffi Enable the Foreign Function Interface (FFI) extension using dev-libs/libffi
fileinfo Enable the File Information extension
filter Enable the Data Filtering extension
firebird Add support for the Firebird relational database
flatfile Add dbm support for flat files
fpm Enable the FastCGI Process Manager SAPI
ftp Add FTP (File Transfer Protocol) support
gd Enable the Image Processing and GD extension (requires media-libs/libjpeg-turbo and media-libs/libpng)
gdbm Add support for sys-libs/gdbm (GNU database libraries)
gmp Add support for dev-libs/gmp (GNU MP library)
iconv Enable support for the iconv character set conversion library
imap Add support for IMAP (Internet Mail Application Protocol)
inifile Add dbm support for .ini files
intl Enables the intl extension for extended internalization support
iodbc Add support for iODBC library
ipv6 Support IPv6 connectivity in fopen and friends, and v6 address conversions in functions like inet_pton and inet_ntop.
jit Enable PCRE JIT support
jpeg Add JPEG image support
kerberos Add kerberos support
ldap Add LDAP support (Lightweight Directory Access Protocol)
ldap-sasl Add SASL support for the PHP LDAP extension using dev-libs/cyrus-sasl
libedit Use the libedit library (replacement for readline)
lmdb Enable support for dev-db/lmdb db backend
mhash Add support for the mhash library
mssql Add support for Microsoft SQL Server database
mysql Add mySQL Database support
mysqli Add support for the improved mySQL libraries
nls Add Native Language Support (using gettext - GNU locale utilities)
oci8-instant-client Use dev-db/oracle-instantclient-basic as Oracle provider instead of requiring a full Oracle server install
odbc Add ODBC Support (Open DataBase Connectivity)
opcache Enables built-in opcode cache, replacing pecl-apc et al.
opcache-jit Enable Just In Time (JIT) compilation within the opcache extension
pcntl Enable the Process Control extension
pdo Enable the PHP Data Objects extension
phar Enables the phar extension to provide phar archive support
phpdbg Enable the PHP Debug Command Line SAPI (like gdb for php)
png Add support for libpng (PNG images)
posix Add support for POSIX-compatible functions
postgres Add support for the postgresql database
qdbm Add support for the qdbm (Quick Database Manager) library
readline Enable support for libreadline, a GNU line-editing library that almost everyone wants
selinux !!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
session Add persistent session support
session-mm Include dev-libs/mm support for session storage
sharedmem Enable the shmop extension
simplexml Enable the SimpleXML extension
snmp Add support for the Simple Network Management Protocol if available
soap Add support for SOAP (Simple Object Access Protocol)
sockets Add support for tcp/ip sockets
sodium Enable support for crypto through dev-libs/libsodium
spell Add dictionary support
sqlite Add support for sqlite - embedded sql database
ssl Add support for SSL/TLS connections (Secure Socket Layer / Transport Layer Security)
systemd Enable use of systemd-specific libraries and features like socket activation or session tracking
sysvipc Enable the PHP System-V semaphore, shared memory and IPC extension
test Enable dependencies and/or preparations necessary to run tests (usually controlled by FEATURES=test but can be toggled independently)
threads Add threads support for various packages. Usually pthreads
tidy Add support for HTML Tidy
tokenizer Add support for the PHP file parser
tokyocabinet Enable support for dev-db/tokyocabinet db backend
truetype Add support for FreeType and/or FreeType2 fonts
unicode Add support for Unicode
valgrind Enable annotations for accuracy. May slow down runtime slightly. Safe to use even if not currently using dev-debug/valgrind
webp Add support for the WebP image format
xml Add support for XML files
xmlreader Enable the XMLReader extension
xmlwriter Enable the XMLWriter extension
xpm Add support for XPM graphics format
xslt Build the XSL extension
zip Enable support for ZIP archives
zlib Add support for zlib compression

The ebuild installs a modified "production" version of php.ini that has tighter security settings and default paths adjusted for Gentoo systems. Both upstream "production" and "development" php.ini files are installed to /usr/share/doc/php-*.


To install extensions, first decide which versions of PHP to compile the extensions for. This is done by setting the PHP_TARGETS variable:

FILE /etc/portage/make.conf

More than one version can be defined; just add in the additional versions separated by a space. Note that the php slot is named "5.6" and the corresponding PHP_TARGETS value is php5-6. This is due to current restrictions on USE names.


After making the above USE flag configurations it is necessary to update the system so the changes take effect:

root #emerge --ask --update --changed-use --deep @world

Running multiple versions of PHP

One of the great advantages of using Gentoo for PHP development is the version slotting. It is very simple to swap between multiple versions of PHP as well as run multiple versions simultaneously. This is all done with the eselect command provided by the app-eselect/eselect-php package which should get emerged in automatically by installing PHP.

For example, selecting different versions of PHP can allow a system to run PHP 7.0 for the cli SAPI but PHP 5.6 for the system's web server. It also allows system administrators or application developers to quickly test an application on different versions of PHP.

To list the available versions for the cli SAPI module use the following syntax:

root #eselect php list cli
 [1]   php5.5 
 [2]   php5.6 *   
 [3]   php7.0

The * (asterisk) marks current active version for the selected module. To check the other SAPIs simply replace cli with fpm,cgi or apache2 modules.

To swap versions, use:

root #eselect php set cli 3

The number 3 in this example corresponds to the number in the output of the list sub-command used above. PHP version 7.0 is now used for the command-line:

root #php -v
PHP 7.0.10-pl0-gentoo (cli) (built: Aug 23 2016 12:38:44) ( NTS )


The PHP configuration is at /etc/php, which contains one subdirectory for each Server API (SAPI) and for each PHP version. For instance, configuration files for the PHP-5.6 apache2 SAPI are installed in /etc/php/apache2-php5.6.

Web servers

To use PHP in a server-side fashion, a web server needs to be installed and configured to use PHP. A number of popular web servers are briefly touched upon next.


Simply emerge nginx to install it:

root #emerge --ask www-servers/nginx
If custom NGINX_MODULES_HTTP values are set in make.conf, make sure that the fastcgi module is enabled.

Once Nginx has been installed, modify the server section of /etc/nginx/nginx.conf to look something like this:

FILE /etc/nginx/nginx.confPart of the nginx configuration to enable PHP through FastCGI
server {
                server_name localhost;
                access_log /var/log/nginx/localhost.access_log main;
                error_log /var/log/nginx/localhost.error_log info;
                root /var/www/localhost/htdocs;
                location ~ \.php$ {
                        try_files $uri $uri/ =404;
                        fastcgi_split_path_info ^(.+\.php)(/.+)$;
                        include fastcgi.conf;

Now start the related services to have a working site. The php-fpm init script starts the PHP FastCGI Process Manager. FastCGI allows web servers to offload the PHP calculations to this process manager.

When running OpenRC as the service manager:

root #rc-service nginx start
root #rc-service php-fpm start

For systemd:

root #systemctl start nginx
root #systemctl start php-fpm@7.2
The version number after the php-fpm service name will change based on the available version of PHP. Adjust as appropriate.


Do not enable the php USE flag for www-servers/lighttpd. It could actually break the build.

Make sure that lighttpd has the php USE flag is disabled:

FILE /etc/portage/package.use
www-servers/lighttpd -php

Lighttpd ships with a default FastCGI config file, but unfortunately, it is written to work with the old PHP FCGI SAPI only, instead of a general FCGI setup. Since the php USE flag has been disabled, it will not be included, and rightly so. However it does provide a good foundation for a configuration file that can be used with FPM.

Edit /etc/lighttpd/mod_fastcgi.conf to look something like this:

FILE /etc/lighttpd/mod_fastcgi.confEnable FastCGI on lighttpd
server.modules += ("mod_fastcgi")
fastcgi.server = ( ".php" =>
  ( "localhost" =>
      "host" => "",
      "port" => "9000"

Note the host and port parts.

Since Gentoo ships with a working php-fpm.ini file, located in /etc/php/fpm-php5/php-fpm.ini, and init script, starting the services is all that is needed:

root #/etc/init.d/php-fpm start
root #/etc/init.d/lighttpd start

Apache (mod_php)

To configure Apache to load the PHP5 module (mod_php), add -D PHP to APACHE2_OPTS variable in /etc/conf.d/apache2. Users might remember that previously, the PHP version had to be added as well (like -D PHP5). However, since app-eselect/eselect-php version 0.8.1, the variable is changed to just -D PHP to allow future major versions to be easily integrated.

FILE /etc/conf.d/apache2Configure Apache to load mod_php
## (settings for PHP5 and above)

Make sure that PHP is built with the apache2 USE flag.

If for some reason the system is missing the PHP module integration file /etc/apache2/modules.d/70_mod_php.conf, currently provided by app-eselect/eselect-php when installed with apache2 USE flag set, manually insert it. Its current content is displayed below.

FILE /etc/apache2/modules.d/70_mod_php.conf
<IfDefine PHP>
	# The symlink is controlled by
	# eselect-php. However, the module name changed from
	# php5_module to php7_module so we can't blindly load whatever
	# is there. Instead we let eselect-php manage a small
	# configuration file that loads the appropriate module.
	Include "/var/lib/eselect-php/mod_php.conf"
	# Tell apache that mod_php should handle PHP files.
	# NOTE: Avoiding AddHandler/AddType for security (bug
	# #538822). Please read the related news item!
	<FilesMatch "\.(php|php[57]|phtml)$">
		SetHandler application/x-httpd-php
	# PHP source files which are meant to be displayed as
	# syntax-highlighted source code.
	<FilesMatch "\.phps$">
		SetHandler application/x-httpd-php-source
	DirectoryIndex index.php index.phtml

Although multiple PHP versions can be installed on a system, Apache can only use a single PHP version with mod_php. Support for multiple PHP versions on Apache is available using fpm. The eselect php command is used to switch between active mod PHP versions.

To change the version of PHP handled by Apache, first list the available versions for the apache2 Server Application Programming Interface (SAPI):

root #eselect php list apache2
 [1]   php5.3
 [2]   php5.4 *
 [3]   php5.5

Change it to the version of choice:

root #eselect php set apache2 N

Substitute N in the example above to the requested number in the output of eselect php list apache2 as displayed earlier on.

To verify the PHP module works, create a test page:

FILE /var/www/localhost/htdocs/index.phpPHP test page
  <?php phpinfo(); ?>

Now, suppress or rename /var/www/localhost/htdocs/index.html and open the test page: http://localhost/

A table describing the PHP settings should be visible.

Apache (fcgid)

See enabling PHP through fcgid in the Apache article.

Apache (mod_proxy_fcgi)

See enabling PHP-FPM through mod_proxy_fcgi in Apache 2.4.

See also

  • Upgrading to PHP 5.6, guide to upgrade older installations to 5.6
  • Upgrading to PHP 7.1, guide to upgrade older installations to 7.1
  • Enabling PHP support in the Apache article
  • Perl — a general purpose interpreted programming language with a powerful regular expression engine.
  • Python — an extremely popular cross-platform object oriented programming language.

External resources