title: PHP files type checking
body: <p>Some weird case when I tried a simple php code to check the file type and it couldn't pass through. Any mistake from the below code ? Thanks in advance.</p>
  
  <pre><code>if(($_FILES["file"]["type"]!="image/jpeg")||
              ($_FILES["file"]["type"]!="image/gif")||
              ($_FILES["file"]["type"]!="image/png")){
              echo "File must be in format of jpeg,gif or png.";
          }
  </code></pre>