In PHP how can I detect when a user is deleting text from an input text field

Question

<form action="" method="POST">
<input type="text" name="phonenumber" value="" />
<form>

If there is something written in the input text field and the user start to delete the string meaning the last letter of the string I want to do something.

So something like this:

if(user deletes last letter of isset($_POST['phonenumber'])){
//do something
}

I tried to use strlen() with -1 but did not seem to work. Anyone have any ideas?

Thank you!

Answer 1

You should use javascript to do something when user is deleting char. One way is to listen to 'keyup' event of the text input. E.g.:

<script>
$(":text[name=phonenumber]").on('keyup', function(event){
   if (event.keyCode == 8){ // means BACKSPACE pressed
        // do something
   }
});
</script>

Answer 2

you can get it by using javascript. on every keyup you have to count the textbox value by id if it is decreasing from the max count means user is deleting some text..

Answer 3

you should use javascript with event keyup ,

jQuery(function($) {
$('input[name=phonenumber]').on('keyup', function(e) {
       if(e.keyCode == 46)
       {
          $.ajax({
             type: 'POST',
             url : 'url',
             data :{'phonenumber': $('input[name=phonenumber]').val()},});
       }
});

});