HTML输入按钮不向我的PHP代码发送任何信号

Question

I've been trying to create a code that accepts user's input and then allows the user to either edit, delete or search all his inputs so far. Here's a snippet of my HTML part that has an error:

<td align = "left"><input type="textarea" name="post" placeholder="What are you thinking? (Only one tag allowed)" style="width: 330px; height: 50px;"  value="<?php echo $post;?>" /> </td>
<td align = "center"><input type="text" name="tag" placeholder="Put your tags here!" style="width: 130px; height: 50px;" value="<?php echo $tag;?>" /> </td>   
            </tr>
        </table>
        <table bgcolor="#004A00" align="center" width="650px">
             <tr>
                <td><br /></td>
            </tr>
            <tr>
              <div align = "center">
            <!-- Input For Add Values To Database-->
            <input type="image" src="http://www.swiftpic.org/image.uploads/06-11-2016/original-655b6e1a6e4b4c149b9969ad99e65699.png"" name="insert">

            <!-- Input For Edit Values -->
            <input type="image" src="http://www.swiftpic.org/image.uploads/06-11-2016/original-80a74827d6700e084482680251134c90.png" name="update">

            <!-- Input For Clear Values -->
            <input type="image" src="http://www.swiftpic.org/image.uploads/06-11-2016/original-02f5a241ad8d3f6c043076e2bb0fce7f.png" name="delete">

            <!-- Input For Find Values With The given ID -->
            <input type="image" height="60px" src="http://www.swiftpic.org/image.uploads/06-11-2016/original-a2aafe78a53258d59b7421b3cf266eb2.png" name="search">
            <a href="?orderBy=date"> Date Ascending:</a>
            <a href="?orderBy1=date"> Date Descending:</a>
       </div>    

I used a code similar to this one before, but without using the images/buttons and it works just fine but when I used these buttons, the PHP code is not receiving any input from the user and therefore won't function after I changed the code.

Any idea on why this is happening? Thanks