PHP: Communicating with an LDAP Server Example

LDAP(Lightweight Directory Access Protocol) is used to talk with directory services for retrieving and modifying data. It is not a relational database system. LDAP is simply a system that provides a hierarchical organization of data. LDAP's most common use currently is for corporate address and email books, allowing for all information about each employee to be stored and retrieved as needed.

PHP provides commands to communicate to an LDAP server that are easy to use. A typical set of commands would be to connect to the server, bind (authenticate), search for some data, and then handle the data. The only problem is that the structure of each LDAP server is completely different based on how the administrator set it up, just like every database system is different. Therefore, you must understand the structure of the tree hierarchy of that LDAP server to work with it.

In the following code, we connect to a fictional LDAP server that just has three levels of hierarchy with the top one being c = Country Code, then under that o = Organization, and then below that un = User Name. (Nominally, of course, there would be more information beneath that level; however, this is all we need for our example.)

<?php
if (!($lc = ldap_connect('ldap.example.com'))) {
    die("ERROR: Can't connect to the LDAP server\n");
}

//Anonymous bind (read only access)
ldap_bind($lc);

// Search for anyone in the IT department
// with a username starting with 'e'
$res = ldap_search($lc, 'o=Information Technology, c=US', 'un=e*');

// Now, let's read all results from our search:
$data = ldap_get_entries($lc, $res);

// Loop over them all, echoing the data out:
for ($i=0; $i < $data['count']; $i++) {
    echo "Full entry (distinguished name - dn): {$data[$i]['dn']}
\n";
    echo "Username: {$data[$i]['un'][0]}
\n";
}
?>

Like many other extensions of the language, LDAP support must be compiled into the server (or enabled on Windows) before you can use it. Also, we have only scratched the surface of what the full LDAP extension can do. To explore more, read the documentation at http://php.net/ldap.

Hope it helps.