ScotlandPHP 2019

Installation of extensions on Windows

After installing PHP and a web server on Windows, you will probably want to install some extensions for added functionality. You can choose which extensions you would like to load when PHP starts by modifying your php.ini. You can also load a module dynamically in your script using dl().

The DLLs for PHP extensions are prefixed with php_.

Many extensions are built into the Windows version of PHP. This means additional DLL files, and the extension directive, are not used to load these extensions. The Windows PHP Extensions table lists extensions that require, or used to require, additional PHP DLL files. Here's a list of built in extensions:

In PHP 4 (updated PHP 4.3.11): BCMath, Caledar, COM, Ctype, FTP, MySQL, ODBC, Overload, PCRE, Session, Tokenizer, WDDX, XML and Zlib

In PHP 5 (updated PHP 5.0.4), the following changes exist. Built in: DOM, LibXML, Iconv, SimpleXML, SPL and SQLite. And the following are no longer built in: MySQL and Overload.

The default location PHP searches for extensions is C:\php4\extensions in PHP 4 and C:\php5 in PHP 5. To change this setting to reflect your setup of PHP edit your php.ini file:

  • You will need to change the extension_dir setting to point to the directory where your extensions lives, or where you have placed your php_*.dll files. For example:

    extension_dir = C:\php\extensions

  • Enable the extension(s) in php.ini you want to use by uncommenting the extension=php_*.dll lines in php.ini. This is done by deleting the leading ; from the extension you want to load.

    Example #1 Enable Bzip2 extension for PHP-Windows

    // change the following line from ...
    // ... to

  • Some of the extensions need extra DLLs to work. Couple of them can be found in the distribution package, in the C:\php\dlls\ folder in PHP 4 or in the main folder in PHP 5, but some, for example Oracle (php_oci8.dll) require DLLs which are not bundled with the distribution package. If you are installing PHP 4, copy the bundled DLLs from C:\php\dlls folder to the main C:\php folder. Don't forget to include C:\php in the system PATH (this process is explained in a separate FAQ entry).

  • Some of these DLLs are not bundled with the PHP distribution. See each extensions documentation page for details. Also, read the manual section titled Installation of PECL extensions for details on PECL. An increasingly large number of PHP extensions are found in PECL, and these extensions require a separate download.

Note: If you are running a server module version of PHP remember to restart your web server to reflect your changes to php.ini.

The following table describes some of the extensions available and required additional dlls.

PHP Extensions
Extension Description Notes
php_bz2.dll bzip2 compression functions None
php_calendar.dll Calendar conversion functions Built in since PHP 4.0.3
php_crack.dll Crack functions None
php_ctype.dll ctype family functions Built in since PHP 4.3.0
php_curl.dll CURL, Client URL library functions Requires: libeay32.dll, ssleay32.dll (bundled)
php_dba.dll DBA: DataBase (dbm-style) Abstraction layer functions None
php_dbase.dll dBase functions None
php_dbx.dll dbx functions  
php_domxml.dll DOM XML functions PHP <= 4.2.0 requires: libxml2.dll (bundled) PHP >= 4.3.0 requires: iconv.dll (bundled)
php_dotnet.dll .NET functions PHP <= 4.1.1
php_exif.dll EXIF functions php_mbstring.dll. And, php_exif.dll must be loaded after php_mbstring.dll in php.ini.
php_fbsql.dll FrontBase functions PHP <= 4.2.0
php_fdf.dll FDF: Forms Data Format functions. Requires: fdftk.dll (bundled)
php_filepro.dll filePro functions Read-only access
php_ftp.dll FTP functions Built-in since PHP 4.0.3
php_gd.dll GD library image functions Removed in PHP 4.3.2. Also note that truecolor functions are not available in GD1, instead, use php_gd2.dll.
php_gd2.dll GD library image functions GD2
php_gettext.dll Gettext functions PHP <= 4.2.0 requires gnu_gettext.dll (bundled), PHP >= 4.2.3 requires libintl-1.dll, iconv.dll (bundled).
php_hyperwave.dll HyperWave functions None
php_iconv.dll ICONV characterset conversion Requires: iconv-1.3.dll (bundled), PHP >=4.2.1 iconv.dll
php_ifx.dll Informix functions Requires: Informix libraries
php_iisfunc.dll IIS management functions None
php_imap.dll IMAP POP3 and NNTP functions None
php_ingres.dll Ingres functions Requires: Ingres libraries
php_interbase.dll InterBase functions Requires: gds32.dll (bundled)
php_java.dll Java functions PHP <= 4.0.6 requires: jvm.dll (bundled)
php_ldap.dll LDAP functions PHP <= 4.2.0 requires libsasl.dll (bundled), PHP >= 4.3.0 requires libeay32.dll, ssleay32.dll (bundled)
php_mbstring.dll Multi-Byte String functions None
php_mcrypt.dll Mcrypt Encryption functions Requires: libmcrypt.dll
php_mhash.dll Mhash functions PHP >= 4.3.0 requires: libmhash.dll (bundled)
php_mime_magic.dll Mimetype functions Requires: magic.mime (bundled)
php_ming.dll Ming functions for Flash None
php_msql.dll mSQL functions Requires: msql.dll (bundled)
php_mssql.dll MSSQL functions Requires: ntwdblib.dll (bundled)
php_mysql.dll MySQL functions PHP >= 5.0.0, requires libmysql.dll (bundled)
php_mysqli.dll MySQLi functions PHP >= 5.0.0, requires libmysql.dll (libmysqli.dll in PHP <= 5.0.2) (bundled)
php_oci8.dll Oracle 8 functions Requires: Oracle 8.1+ client libraries
php_openssl.dll OpenSSL functions Requires: libeay32.dll (bundled)
php_overload.dll Object overloading functions Built in since PHP 4.3.0
php_pdf.dll PDF functions None
php_pgsql.dll PostgreSQL functions None
php_printer.dll Printer functions None
php_shmop.dll Shared Memory functions None
php_snmp.dll SNMP get and walk functions NT only!
php_soap.dll SOAP functions PHP >= 5.0.0
php_sockets.dll Socket functions None
php_sybase_ct.dll Sybase functions Requires: Sybase client libraries
php_tidy.dll Tidy functions PHP >= 5.0.0
php_tokenizer.dll Tokenizer functions Built in since PHP 4.3.0
php_w32api.dll W32api functions None
php_xmlrpc.dll XML-RPC functions PHP >= 4.2.1 requires: iconv.dll (bundled)
php_xslt.dll XSLT functions PHP <= 4.2.0 requires sablot.dll, expat.dll (bundled). PHP >= 4.2.1 requires sablot.dll, expat.dll, iconv.dll (bundled).
php_yaz.dll YAZ functions Requires: yaz.dll (bundled)
php_zip.dll Zip File functions Read only access
php_zlib.dll ZLib compression functions Built in since PHP 4.3.0

add a note add a note

User Contributed Notes 16 notes

jwagner at digilog dot de
4 years ago
On Windows hosts libeay32.dll and ssleay32.dll have to be path-accessible for php_curl.dll to work correctly. Copying them into System32 (or even into the Windows main directory) is a bad hack (and does not even work with newer PHP versions). The right way to do it, is to add the PHP path to the Windows *Path* variable. In *Control Panel* --> *System* click on *Advanced System Settings* and use the button *Environment Variables*. Under *System Variables* you will find the *Path* variable. Edit it and append `;C:/PHP` to it - or whatever the path to your PHP root folder is.
smaines at alaya dot com
10 years ago
== Problem

Consider the following from an httpd.conf file...

  LoadModule php5_module "E:/xyz/php/php5apache2_2.dll"
  PHPIniDir "E:/xyz/php"

...which led to the dreaded...

  PHP Warning:  PHP Startup: Unable to load dynamic library 'E:\\xyz\\php\\ext\\php_mysql.dll' - The specified module could not be found.

Note, however, that PHP.exe apparently was found and executed php pages in Apache, but the MySQL functions therein failed.

== Solution

Because PHP dir was not in $PATH, php5apache2_2.dll failed to find php_mysql.dll (the only extension I enabled) during Apache 2.2 start.

== Caveat (!)

The BIG issue is that, setting $PATH in...

  <desk icon>My Computer
  <rt click>Properties
  <button>Environment Variables

...didn't export the $PATH change such that restarting the Apache service (in MMC) would pick it up.  So I tested the working solution (adding PHP dir to $PATH), but it failed because of HOW I set it. It succeeded only when I REBOOTED after changing the $PATH.  There may be an easier way that this, but I do not know it at present.

== Comment

Consider whether PHP dir should need to be in $PATH at all, when PHP.exe apparently was found and executes php pages in Apache, but php5apache2_2.dll failed to find whatever was needed to load the extensions.  This should perhaps be addressed.

Note that on a WAMP installation (W2K,Apache,MySQL,PHP), only PHP is required in $PATH.
10 years ago
I just recently tried to upgrade my php install on WinXP using the php-5.2.6-win32-installer.msi and with fingers crossed, tried to see if things still worked or not.

Unfortunately, they didn't.  I did see many posts here and elsewhere on the web regarding the error message:

"Unable to load dynamic link library 'ext\php_xxxxx.dll' - The specified module could not be found." says in the past when upgrading to simply copy over new php files, but now recommends using the windows installer.  Maybe the installer isn't quite up to the task yet.

My fix:

1. Completely uninstall current version of php (using Windows Control Panel > Add or Remove Programs).

2. Download the current php binaries for Windows (at under Windows Binaries).  Should be format: PHP 5.x.x zip package.  Again, download the binaries, NOT the installer.

3. Follow these easy steps

4. Set your PATH for Windows to find php (if you haven't already):
a. Right-click on My Computer
b. Properties
c. Advanced Tab > Environment Variables
d. Under System variables, scroll down to find "Path", select and click on Edit
e. Add path to your php install on the end (make sure to precede with semi-colon ";").  Mine was ";G:\Apache\php"
f. Click Okay.  (then "Okay" on each of the other open windows).

5. Test php install. (see ricocheting link above for testing).

6. Getting the extensions to work again:
a. Open php.ini
b. uncomment each extension, restart Apache.

7. Special note on libmysql.dll and problems getting MySQL to work:
- You may have copied over this file into your Windows/System32 (or WINNT/System32 for me) to get mysql to work in the past.  If so, replace it with the most recent version you get with the upgrade (in top dir).
- If this is a fresh install, copy the libmysql.dll into your System32 folder.

Couple notes:
1. The above tutorial link is to install php 5.x on Apache 2.2 for Win.  If you're running Apache 2.0 like me, pay special attention to "Editing Apache Conf File" for correct LoadModule info.
2. If you ran the installer previously, double check your Apache conf where the php5 LoadModule stuff is.  The installer might have messed with this a bit.

I hope this stuff helps.
guy dot paddock at redbottledesign dot com
3 years ago
Note that if you're trying to install PECL HTTP on Windows, you will need to install:

- php_http
- php_ssh2
- php_propro
- php_raphf

Make sure that all plug-ins were compiled for your version of PHP (version number, whether or not it's thread-safe, etc). Otherwise, they will fail to load.

The version of PHP that comes with Acquia Dev Desktop is the thread-safe version, so all plug-ins must be thread safe (TS). I had to use an older release of php_http (2.3.2) to get the TS version.

For the other extensions, I had to make sure some of them loaded BEFORE php_http in the php.ini file:

vatozana at yahoo dot com
8 years ago
I had problems registering Curl extentions and it was cause by the old dll of libeay32.dll and  ssleay32.dll  which were already in my c:\windows\system32 I replaced them and all is now fine!!
9 years ago
I had problem with extensions - they don't loaded (without errors) on Windows installation and don't displayed in phpinfo().

Solve: full-specified directory name for extension_dir directive - "c:/php/ext/" instead "./"
ole berge at web de
4 years ago


Windows Server 2012 R 64 bit
4 years ago
If you have problems, that windows-extensions can not be loaded (PHP Warning: PHP Startup: Unable to load dynamic library) and you are sure, the .ddl is in the right place, use ProcessMonitor (

here you can see at startup, which files php tries to find and in which locations php tries to find them!
alx dot suvorov at gmail dot com
10 months ago
To enable PDO drivers for PHP 7 on Windows:

1. Specify full path to extensions in "php.ini", e.g.:
extension_dir = "c:/alex/apps/php-7.2.3/ext/"

2. Specify to load specific PDO extension, e.g.:

Save. Restart the web server and it should work.
admin at artiststechguy dot com
2 years ago
After much searching I discovered the reason why my dll was not found was simply because an old version of easy-php had left an entry in the path variable which was being used instead of the entry I added at the end.

tl;dr - search your path variable for old versions of php and delete them.
Manda Krishna Srikanth
10 years ago
As far as my experience says, 95% of ext\php_mysql.dll - The specified module could not be found - error can be sorted out on Win 2003, IIS 6, PHP5.2.

Replace the php_mysql.dll and libmysql.dll downloaded from into extensions directory.

For MSSQL connectivity problems, replace the ntwdblib.dll in php dir with the one copied from system32 directory. Ofcourse the filesize will be less, no problem, replace it.
11 years ago
Installing PHP extensions for IIS for the first time is sort of a baptism by fire -- you will get your hands dirty, and other suitable metaphors of nastiness.  Hopefully, you won't have to spend too many days googling around fora and restarting IIS 10 million times as I did until I finally realized both what was going on and what crazy things I'd done wrong.

THIS (peter)guy really goes into terrific detail and troubleshooting, (with very good reasons and explanations of extension dependencies not listed on the current php page you're now reading):

Most of this is applicable for IIS5.1 as well, as far as I've found.

The main problem I'd been butting my head up against was extensions being reported as not found, even though the .DLLs were definitely in C:\PHP\ext, and my PATH env var was setup correctly. 

The error messaging during dynamic loading of implicitly-linked libraries should be more specific, telling you that in fact it is a particular dependency of a dependency which is missing -- usually some obscure third-party .dll -- and name it!

Eventually I stopped being so greedy and just cut down on the extensions I thought I needed by commenting them out in php.ini.  That eliminated the startup errors.  Apparently some of these extensions or their requirements, which either come with the base PHP install zip or the PECL extensions, are either too obscure or too fragile to be necessary anyway.

Good luck, and I hope anyone who runs into the same trouble can hit upon this or Peter Guy's page directly before they go too crazy.
simi_def at c2 dot hu
12 years ago
I had problems with PHP5/Apache2.2/MySQL 5 installation on a WinXp machine.

I got the

Fatal error: call to undefined function - mysql_connect().


Solution :
1, use correct version of ext\php_mysql.dll and libmysql.dll
2, !!! edit the CORRECT php.ini (%windir%\php.ini) like c:\windows\php.ini !!!
3, add php installation dir to PATH
4, edit php.ini to load extension php_mysql.dll

to check.
9 years ago
I had a problem with the gd and mysqli mods on my PHP5.2/Apache2.2/Windows 2003 server. Even after enabling the options in the php.ini file and restarting the Apache service, the mods still would not load. I even tried to restart the Windows 2003 server that php is loaded on - and no go. After reviewing the system path variables in Windows, I noticed that the c:\php directory was set in the path variable, but not the folder for the gd, mysqli and others mods. So I added c:\php\ext to the path variable and rebooted the server. THAT FIXED IT!!
jma59 at cam dot ac dot uk
11 years ago
Under windows, given an error similar to

PHP Warning:  PHP Startup: Unable to load dynamic library 'c:\\php\\ext\\php_mysql.dll' - The specified module could not be found.\r\n in Unknown on line 0

When PHP definitely should be able to find the module, it's fairly common knowledge that this error can also be caused by  certain dlls not being in the PATH. These dlls (usually libeay32 and ssleay32) are generally found in your base php directory, and the modern windows installers add the base php directory to the PATH so that you don't need to worry about it. However, if when installing earlier versions you decided on moving libeay32, ssleay32 et al to C:\Windows\System32 instead of changing the PATH, then php will still end up with the old versions and the out of date versions will cause the same error as above. Don't fall into the trap like I did.
rafaurl at gmail dot com
8 years ago
I got the following error:

PHP Warning:  PHP Startup: Unable to load dynamic library 'C:\PHP\ext\php_curl.dll'

By using sysinternals procmon I saw that it failed after trying to load "zlib.dll". I found this file deployed with other software (in my case, Miranda IM) and copied it to the PHP installation directory. It worked fine after that. Hope that helps.
To Top