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The Zend_Auth_Adapter_Ldap constructor accepts three parameters.

The $options parameter is required and must be an array containing one or more sets of options. Note that it is an array of arrays of Zend_Ldap options. Even if you will be using only one LDAP server, the options must still be within another array.

Below is print_r() output of an example options parameter containing two sets of server options for LDAP servers and (the same options as the above INI representation):

    [server2] => Array
            [host] =>
            [useStartTls] => 1
            [accountDomainName] =>
            [accountDomainNameShort] => W
            [accountCanonicalForm] => 3
            [baseDn] => CN=Users,DC=w,DC=net

    [server1] => Array
            [host] =>
            [accountDomainName] =>
            [accountDomainNameShort] => FOO
            [accountCanonicalForm] => 3
            [username] => CN=user1,DC=foo,DC=net
            [password] => pass1
            [baseDn] => OU=Sales,DC=foo,DC=net
            [bindRequiresDn] => 1


The information provided in each set of options above is different mainly because AD does not require a username be in DN form when binding (see the bindRequiresDn option in the Server Options section below), which means we can omit a number of options associated with retrieving the DN for a username being authenticated.

What is a Distinguished Name?

A DN or "distinguished name" is a string that represents the path to an object within the LDAP directory. Each comma-separated component is an attribute and value representing a node. The components are evaluated in reverse. For example, the user account CN=Bob Carter,CN=Users,DC=w,DC=net is located directly within the CN=Users,DC=w,DC=net container. This structure is best explored with an LDAP browser like the ADSI Edit MMC snap-in for Active Directory or phpLDAPadmin.

The names of servers (e.g. 'server1' and 'server2' shown above) are largely arbitrary, but for the sake of using Zend_Config, the identifiers should be present (as opposed to being numeric indexes) and should not contain any special characters used by the associated file formats (e.g. the '.' INI property separator, '&' for XML entity references, etc).

With multiple sets of server options, the adapter can authenticate users in multiple domains and provide failover so that if one server is not available, another will be queried.

The Gory Details: What Happens in the Authenticate Method?

When the authenticate() method is called, the adapter iterates over each set of server options, sets them on the internal Zend_Ldap instance, and calls the Zend_Ldap::bind() method with the username and password being authenticated. The Zend_Ldap class checks to see if the username is qualified with a domain (e.g., has a domain component like or FOO\alice). If a domain is present, but does not match either of the server's domain names ( or FOO), a special exception is thrown and caught by Zend_Auth_Adapter_Ldap that causes that server to be ignored and the next set of server options is selected. If a domain does match, or if the user did not supply a qualified username, Zend_Ldap proceeds to try to bind with the supplied credentials. if the bind is not successful, Zend_Ldap throws a Zend_Ldap_Exception which is caught by Zend_Auth_Adapter_Ldap and the next set of server options is tried. If the bind is successful, the iteration stops, and the adapter's authenticate() method returns a successful result. If all server options have been tried without success, the authentication fails, and authenticate() returns a failure result with error messages from the last iteration.

The username and password parameters of the Zend_Auth_Adapter_Ldap constructor represent the credentials being authenticated (i.e., the credentials supplied by the user through your HTML login form). Alternatively, they may also be set with the setUsername() and setPassword() methods.

Zend Framework