PHP LDAP登录问题

我的PHP LDAP登录有点问题。我的第一次绑定成功，但即使凭据正确，我的第二次绑定也不成功。我试着在第一个绑定中使用我用于第二个绑定的凭据来确保它有效，并且确信它可以在第一个时绑定它。为什么我不能第二次绑定？

<?php
// Define $myusername and $mypassword
$username=$_POST['username'];
$password=$_POST['password'];
// using ldap bind
$ldaprdn  = 'uid=MYUID,ou=special,ou=people,o=myo.com,dc=mydc,dc=com';     // ldap rdn or dn
$ldappass = 'PASSWORD';  // associated password
// connect to ldap server
$ldapconn = ldap_connect("ldaps://MYLDAPSERVER", ###)
    or die("Could not connect to LDAP server.");
if ($ldapconn) 
{
    // binding to ldap server
    $ldapbind = ldap_bind($ldapconn, $ldaprdn, $ldappass);
    // verify binding
    if ($ldapbind) 
    {
        $result = ldap_search($ldapconn, "ou=people,o=myo.com,dc=mydc,dc=com", "uid=$username");
        $info = ldap_get_entries($ldapconn, $result);
        $userdn = $info[0]["dn"];
        $count = $info["count"]; 
        ldap_unbind($ldapconn);
        if ($count == 1)
        {
            $ldapbinduser = ldap_bind($ldapconn, $userdn, $password);
            if ($ldapbinduser) 
            {
                echo "Sucess you made it all the way<br />";
            }
            else
            {
                echo "Invalid Login Details, please try again(1001)";
            }
        }
        else
        {
            echo "Invalid Login Details, please try again(1002)";
        }
    } 
    else 
    {
        echo "LDAP bind failed(1000)";
    }
}