<form action="?action7" method="POST">
    <label for="fname">
        Update image
    </label>
    <input type="file" name="image">
    <input type="submit" name="submit" value="Submit">
    <?php
      if(isset($_GET['action7'])=='rdt')
      { 
         $image= addslashes($_FILES['image']['tmp_name']);
         $image= file_get_contents($image);
         $image= base64_encode($image);
         saveimage($image);
      }
      function saveimage($image)
      {
         $con=mysqli_connect("localhost","root","","mydb");
         mysqli_select_db($con,"photos");
         $qry="update images102 set image='$image' where email='$picmail'";
         $result=mysqli_query($con,$qry);
         if($result)
         {
             echo "image uploaded.";
         }
         else
         { 
             echo "image not uploaded";
         }
      }
    ?>
</form>

请注意： $picmail 是在此代码函数外部声明的全局变量。执行显示消息 "Image uploaded" . 但是，数据库显示旧图像中没有任何更改