You would think that simply authenticating a user in Active Directory would be a pretty simple process using LDAP in PHP without the need for a library. But there are a lot of things that can complicate it pretty fast:

• You must validate input. An empty username/password would pass otherwise.
• You should ensure the username/password is properly encoded when binding.
• You should be encrypting the connection using TLS.
• Using separate LDAP servers for redundancy in case one is down.
• Getting an informative error message if authentication fails.

It's actually easier in most cases to use a LDAP library supporting the above. I ultimately ended up rolling my own library which handles all the above points: LdapTools (Well, not just for authentication, it can do much more). It can be used like the following:

use LdapTools\Configuration;
use LdapTools\DomainConfiguration;
use LdapTools\LdapManager;

$domain = (new DomainConfiguration('example.com'))
    ->setUsername('username') # A separate AD service account used by your app
    ->setPassword('password')
    ->setServers(['dc1', 'dc2', 'dc3'])
    ->setUseTls(true);
$config = new Configuration($domain);
$ldap = new LdapManager($config);

if (!$ldap->authenticate($username, $password, $message)) {
    echo "Error: $message";
} else {
    // Do something...
}

The authenticate call above will:

• Validate that neither the username or password is empty.
• Ensure the username/password is properly encoded (UTF-8 by default)
• Try an alternate LDAP server in case one is down.
• Encrypt the authentication request using TLS.
• Provide additional information if it failed (ie. locked/disabled account, etc)

There are other libraries to do this too (Such as Adldap2). However, I felt compelled enough to provide some additional information as the most up-voted answer is actually a security risk to rely on with no input validation done and not using TLS.

I do this simply by passing the user credentials to ldap_bind().

If the account can bind to LDAP, it's valid; if it can't, it's not. If all you're doing is authentication (not account management), I don't see the need for a library.

I like the Zend_Ldap Class, you can use only this class in your project, without the Zend Framework.

PHP has libraries:

PEAR also has a number of packages:

I haven't used either, but I was going to at one point and they seemed like they should work.

For those looking for a complete example check out .

I have tested this connecting to both Windows Server 2003 and Windows Server 2008 R2 domain controllers from a Windows Server 2003 Web Server (IIS6) and from a windows server 2012 enterprise running IIS 8.