PHP Read input from user

I try open url from user input value but its no value

<form>
<p>*number:</p>

  <input type="text" name="numberpage" value=""/>

</form>
<a  href="./page.php?page=editdatapo&id=<?php echo $_POST['numberpage']; ?>">find</a>

here result that should be

user input = 13

output url

localhost/page.php?page=editdatapo&id=13

but output like this

localhost/page.php?page=editdatapo&id=

Answer

<form action="./page.php" method="GET">
   <p>*number:</p>
   <input type="hidden" name="page" value="editdatapo" />
   <input required type="text" name="id"/>
   <input type="submit" value="Find" />
</form>

Try using GET. After hitting submit, it will redirect to:

page.php?page=editdatapo&id=USER_INPUT

This way, you dont have to use $_POST just to access the link. You can just type the id then hit Enter/Find directly.

By default, forms without the method attribute uses GET and you can omit it if you really want to.