Single Sign On with Active Directory Using LDAP - php

Question

I am trying to get user information from LDAP function. I need a single sign in for my PHP application on Active Directory. I am using following function:
$ldapserver = 'abc.com';
$ldapuser = 'ali#abc.com';
$ldappass = 'xyz';
$attributes_ad = array
("displayName","description","cn","givenName","sn","mail","co","mobile","company","
displayName");
// define base
$base ="";
// connect
$ldapconn = ldap_connect($ldapserver) or die("Could not connect to LDAP server.");
if($ldapconn) {
// binding to ldap server
$ldapbind = ldap_bind($ldapconn, $ldapuser, $ldappass) or die ("Error trying to
bind: ".ldap_error($ldapconn));
// verify binding
if ($ldapbind) {
echo "LDAP bind successful...<br /><br />";
$result = ldap_search($ldapconn, $base, "mail=$email*", $attributes_ad) or die ("Error in search
query");
$info = ldap_get_entries($ldapconn, $result);
//Now, to display the results we want:
for ($i=0; $i<$info["count"]; $i++)
{
// to show the attribute displayName (note the case!)
echo $info[$i]["displayname"][0];
}
}
}
Above code requires username and password both but I need a solution that can get the username and password whenever someone will login with AD credentials I need to use them to authenticate my login for my PHP application (actually it is an intranet application). Please help me with that I need to fetch all available user info from active directory.