php如何判斷正常訪問和外部存取

<?php  session_start();  if(isset($_POST['check'])&&!empty($_POST['name'])){      if($_POST['check'] == $_SESSION['check']){          echo "正常訪問";      }else{          echo "外部存取";      }  }      $token = md5(uniqid(rand(),true));      $_SESSION['check'] = $token;  ?>  <form method="post" action="">  <input type="text" name="name" />  <input type="text" name="check" value="<?=$token;?>">  <input type="submit">