INTEGRATING ACTIVE DIRECTORY WITH PHP-LDAP AND TLS 
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My configuration:
Apache/2.2.14 (Win32) mod_ssl/2.2.14 OpenSSL/0.9.8k PHP/5.2.11
NOTE 1: At the momment, the versión 5.3.1 fail with tls
NOTE 2: This example works on windows, but in linux is similar
1) Download the Certificate X.509 (PEM format) from a web browser, I used Firefox. I put the name webcert.crt
2) Create the folder c:\openldap\sysconf
3) Copy the file webcert.crt to c:\openldap\sysconf
4) With notepad you must create the file c:\openldap\sysconf\ldap.conf file. The file contents:
TLS_REQCERT never
TLS_CACERT c:\openldap\sysconf\webcert.crt
5) The code:
<?php
   $ldap="ldap.myDomain.com";
   $usr="user@myDomain.com";
   $pwd="mypassword";
   
   $ds=ldap_connect($ldap);  
   $ldapbind=false;
   if(ldap_set_option($ds, LDAP_OPT_PROTOCOL_VERSION, 3))
      if(ldap_set_option($ds, LDAP_OPT_REFERRALS, 0)) 
         if(ldap_start_tls($ds)) 
               $ldapbind = @ldap_bind($ds, $usr, $pwd);    
   ldap_close($ds);
   if(!$ldapbind)
       echo "ERROR";
   else
       echo "OK";
?>