I installed Moodle 1.9.4+ (Build: 20090329) on the Mac OS X 10.5.6 Server with PHP 5.2.9.
Please look at http://docs.moodle.org/en/Step_by_Step_Installation_on_a_Mac_OS_X_10.5_Server

 I installed Moodle 1.9.4+ (Build: 20090329) because I wanted to update to Moodle 2.0.
It could be that this problem is the same as I wrote in http://tracker.moodle.org/browse/MDL-18737

Moodle 1.9.4+ works fine but upgrading to Moodle 2.0 does not work. I get the following error message

__________________________________________________________________________________________
|
| Error: Database connection failed
| It is possible that the database is overloaded or otherwise not running properly.
| The site administrator should also check that the database details have been correctly specified in config.php
|__________________________________________________________________________________________

Moodle uses the normal config.php (the names are moodle20 because I want to update)

<?php /// Moodle Configuration File

unset($CFG);

$CFG->dbtype = 'mysql';
$CFG->dbhost = 'localhost';
$CFG->dbname = 'moodle20';
$CFG->dbuser = 'moodle';
$CFG->dbpass = 'moodle!';
$CFG->dbpersist = false;
$CFG->prefix = 'mdl_';

$CFG->wwwroot = 'http://192.168.0.220/moodle20';
$CFG->dirroot = '/Library/WebServer/Documents/moodle20';
$CFG->dataroot = '/Library/WebServer/moodledata/moodle20';
$CFG->admin = 'admin';

$CFG->directorypermissions = 00777; // try 02777 on a server in Safe Mode

require_once("$CFG->dirroot/lib/setup.php");
// MAKE SURE WHEN YOU EDIT THIS FILE THAT THERE ARE NO SPACES, BLANK LINES,
// RETURNS, OR ANYTHING ELSE AFTER THE TWO CHARACTERS ON THE NEXT LINE.
?>