A quick set of instructions for installing PEAR on OS X 10.5 (Leopard):
PHP’s PEAR repository does not come with Leopard but it only takes about five minutes, if that, to install.
Download the PEAR install package:
$ curl http://pear.php.net/go-pear > go-pear.php
Run the installer as superuser:
$ sudo php -q go-pear.php
If your behind a proxy/firewall you can enter the required details when the following prompt appears:
HTTP proxy (http://user:password@proxy.myhost.com:port), or Enter for none:
The PEAR installer will suggest a file layout similar to the following, we need to change the installation prefix (see below):
 1. Installation prefix ($prefix) : /Users/usrname
 2. Temporary files directory    : $prefix/temp
 3. Binaries directory           : $prefix/bin
 4. PHP code directory ($php_dir) : $prefix/PEAR
 5. Documentation base directory : $php_dir/docs
 6. Data base directory          : $php_dir/data
 7. Tests base directory         : $php_dir/tests
Change the installation prefix to ‘/usr/local’:
1-7, 'all' or Enter to continue: 1
Installation prefix ($prefix) [/Users/awmstrs] : /usr/local
Choose whether or not to install optional bundled packages when the following prompt appears (see PEAR‘s site for more info) :
The following PEAR packages are bundled with PHP: PEAR_Frontend_Web-beta, PEAR_Frontend_Gtk2, MDB2.
Would you like to install these as well? [Y/n] :
Allow the install script to alter the php.ini file or make the changes yourself (see http://clickontyler.com/):
Would you like to alter php.ini </private/etc/php.ini>? [Y/n] : Y
That’s it – as the script says:
The 'pear' command is now at your service at /usr/local/bin/pear
Thanks to http://clickontyler.com/ for pointing me in the right direction.