If you have Ubuntu (I know 10.04+, not sure about earlier), you can do this to install the package;
sudo apt-get php5-svn
Information for installing this PECL extension may be found in the manual chapter titled Installation of PECL extensions. Additional information such as new releases, downloads, source files, maintainer information, and a CHANGELOG, can be located here: ยป http://pecl.php.net/package/svn
If ./configure is having trouble finding the
SVN files (for example, Subversion was installed with a
different prefix directory), use
./configure --with-svn=$USR_PATH
to specify the directory where the
include/subversion-1/ folder is located.
A DLL for this PECL extension is currently unavailable. See also the building on Windows section.
If the extension is compiled against libsvn 1.3, functions that work with working copies will fail when used on working copies created by Subversion 1.4.
If you have Ubuntu (I know 10.04+, not sure about earlier), you can do this to install the package;
sudo apt-get php5-svn
For install in CentOS 5.5
yum install subversion subversion-devel neon neon-devel
pecl install svn
echo "extension=svn.so" > /etc/php.d/svn.ini
service httpd restart
If you use CollabNet's Subversion client (v. 1.6.13), the development libraries are included. For the most current version (v 1.6.17) you may need to install CollabNet Subversion Edge for access to the development libraries.
Sure, the subversion-devel package should not conflict with Collabnet, but it has a dependency with the subversion package, which installs svn binaries in /usr/bin, which takes precedence over CollabNet's path in the PATH environment variable.
For Windows:
If you use a fresh install of windows XP you will need all this DLL in your C:/windows/system32/ folder:
intl3_svn.dll, libdb43.dll, libapr.dll, libapriconv.dll, libaprutil.dll, libeay32.dll, msjava.dll, php5ts.dll, ssleay32.dll, vsinit.dll, msvcr71.dll, MSVCP71.DLL
I recommend to use DependencyWalker (http://www.dependencywalker.com/) with your php_svn.dll (in php extensions) to see exactly which ones you need.