What could have gone wrong?

Question

I installed PHP 4.4.6 + Oracle instant client 10g(win32) + Apache 2.0.59 (Win32) on my Windows XP Professional Version 2002 SP2.
I enabled php_oci8.dll in my php.ini. Also put tnsname.ora under C:\instantclient_10_2.
I loaded phpinfo.php and it shows "OCI8 Support      enabled"
However when I use below script to test:
<?php
if ($c=OCILogon("user", "pw", "db")) {
echo "Successfully connected to Oracle.\n";
OCILogoff($c);
} else {
$err = OCIError();
var_dump($err);
print "\nError code = " . $err;
  print "\nError message = "  . $err[message];
  print "\nError position = " . $err[offset];
  print "\nSQL Statement = "  . $err[sqltext];
  echo "\nOracle Connect Error " . var_dump( OCIError() );
?>
The output is:
Interactive mode enabled
bool(false)
Error code =
Error message =
Error position =
SQL Statement = bool(false)
Oracle Connect Error
Please help enlighten what I should do to move on.
Many thanks,
PHPNewbie                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Answer 1

Thanks cj. I think I'm getting closer.
After replaced php_oci8.dll, I retested a simplified script:
if ($c=OCILogon("user", "pw", "kirin"))
{ echo "Successfully connected to Oracle.\n";
OCILogoff($c); }
else { $err = OCIError();
var_dump($err);
#echo "\nOracle Connect Error " . var_dump( OCIError() );
?>
The the output is:
Warning: ocilogon() [function.ocilogon]: OCIEnvInit() failed. There is something wrong with your system - please check that ORACLE_HOME is set and points to the right directory in C:\work\test.php on line 3
Warning: ocierror() [function.ocierror]: OCIError: unable to find error handle in C:\work\test.php on line 6
bool(false)
I can't understand both warnings, isn't that ORACLE_HOME is not needed for instant client, For the second warning, isn't that OCIError does not need to pass any handle?