Php – ldap_bind(): Unable to bind to server: Can’t contact LDAP server

I can remote access in using the admin username and password which I'm using the same username and password in the script. but I get the following error

Warning: ldap_bind(): Unable to bind to server: Can't contact LDAP server in

Could not bind to the server. Check the username/password.
Server Response:
Error Number: -1
Description: Can't contact LDAP server

<?php
    ini_set('display_errors',1);
    ini_set('display_startup_errors',1);
    error_reporting(-1);

     // Username used to connect to the server
     $username = "Administrator";

     // Password of the user.
     $password = "password";

     // Either an IP or a domain.
     $ldap_server = "10.10.10.10";

     // Get a connection
     $ldap_conn = ldap_connect($ldap_server);

     // Set LDAP_OPT_PROTOCOL_VERSION to 3
     ldap_set_option($ldap_conn, LDAP_OPT_PROTOCOL_VERSION, 3) or die ("Could not set LDAP Protocol version");

     // Authenticate the user and link the resource_id with
     // the authentication.
     if($ldapbind = ldap_bind($ldap_conn, $username, $password) == true)
     {
     // Setup the data that will be used to create the user
     // This is in the form of a multi-dimensional
     // array that will be passed to AD to insert.
     $adduserAD["cn"] = "testuser";
     $adduserAD["sn"] = "User";
     $adduserAD["samaccountname"] = "testuser";
     $adduserAD["objectClass"] = "user";
     $adduserAD["displayname"] = "Test User";
     $adduserAD["userPassword"] = "Welcome123!";
     $adduserAD["userAccountControl"] = 544;

     $base_dn = "cn=testuser,cn=Users,DC=testdomain,DC=com";

     // Display some "waiting" text.
     echo "Trying to add the user to the system ...<br>";

     // Attempt to add the user with ldap_add()
     if(ldap_add($ldap_conn, $base_dn, $adduserAD) == true)
     {

     // The user is added and should be ready to be logged
     // in to the domain.
     echo "User added!<br>";
     }else{

     // This error message will be displayed if the user
     // was not able to be added to the AD structure.
     echo "Sorry, the user was not added.<br>Error Number: ";
     echo ldap_errno($ldap_conn) . "<br />Error Description: ";
     echo ldap_error($ldap_conn) . "<br />";
     }
     }else{
     echo "Could not bind to the server. Check the username/password.<br />";
     echo "Server Response:"

     // Error number.
     . "<br />Error Number: " . ldap_errno($ldap_conn)

     // Error description.
     . "<br />Description: " . ldap_error($ldap_conn);
     }

     // Always make sure you close the server after
     // your script is finished.
     ldap_close($ldap_conn);
    ?>