Required PHP Extensions For WordPress – WPQuickies

In this lunchtime WPQuickies, I’ll be listing the required PHP extensions that WordPress needs to run properly.

How Do WordPress and PHP Work Together?
Here’s a diagram of a very simplified WordPress PHP stack.

WordPress is an event-driven app built in PHP.

PHP is a dynamic language that compiles code in real-time to generate HTML as an output.

For the WordPress stack, most of the dynamic data come from functions and a database.

The output is sent to the webserver and along with static assets such as image files, CSS files, JavaScript files, the web server creates the final full web page and sends that back to the requesting browser.
What Are PHP Extensions?

Similarly to extending WordPress core functionality by installing plugins, the core PHP programming language can gain additional functionality by using extensions.

PHP extensions are compiled libraries installed in a folder within the PHP installation folder. The extract folder name is specified in the php.ini configuration file – there is no default extension folder file or pathname.

To find the folder on Linux-based installations, from the command line you can type:
php -i | grep extension_dir

On other operating systems, you can look directly in the php.ini configuration file to locate the extensions directory.

How Many PHP Extensions Exist?

According to the PHP documentation ref: there are 176 officially documented PHP extensions.

What PHP Extensions Are Needed For WordPress?

According to the WordPress handbook, WordPress needs:

• 13 official PHP extensions for core functionality (pink)
• 9 official PHP extensions for fallback functions (orange)
• 3 official PHP extensions if files are non-writable on the server (yellow)
• 1 non-official PHP extension (blue)

What Do These PHP Extensions Do?

Here’s what these core PHP extensions do.

• curl
  Performs remote request operations.
• dom
  Used to validate Text Widget content and to automatically configure IIS7+.
• exif
  Works with metadata stored in images.
• fileinfo
  Used to detect mime type of file uploads.
• hash
  Used for hashing, including passwords and update packages.
• imagick
  Provides better image quality for media uploads.
• json
  Used for communications with other servers.
• mbstring
  Used to properly handle UTF 8 text.
• mysqli
  Connects to MySQL for database interactions.
• openssl
  Permits SSL-based connections to other hosts.
• pcre
  Increases performance of pattern matching in code searches.
• sodium
  Validates Signatures and provides secure random bytes.
• xml
  Used for XML parsing, such as from a third-party site.
• zip
  Used for decompressing Plugins, Themes, and WordPress update packages.

Fallback PHP Extensions

These are fallback PHP extensions, used if the core extensions are not implemented – i.e. perhaps you are running an out-of-date PHP version.

• bcmath
  For arbitrary precision mathematics.
• filter
  Used for securely filtering user input.
• gd
  If Imagick isn’t installed, the GD Graphics Library is used 
• iconv
  Used to convert between character sets.
• intl
  Enable to perform locale-aware operations.
• mcrypt
  Generates random bytes when libsodium and /dev/urandom aren’t available.
• simplexml
  Used for XML parsing.
• xmlreader
  Used for XML parsing.
• zlib
  Gzip compression and decompression.

PHP Extensions Used For File Changes

These PHP extensions are used when the file system can’t modify a file directly.

• ssh2
  Provide access to remote machine resources (shell, remote exec, file transfer)
• ftp
  Implement client access to files servers speaking the File Transfer Protocol (FTP).
• sockets
  Implements a low-level interface to the socket communication functions 

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