showing sweet alert after php database record delete

Black Sulfur
Black Sulfur used Ask the Experts™
on
After I click on a button to delete a single record, I want a sweet alert to display but I don't know if it can be done using php or if it would have to be done using ajax?

This is the button which is in a form with method of "post":

 <input type="submit" class="btn btn-danger btn-fill" name="delete_comment" value="Delete message">

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Here is my function:

function delete_contact_message($link) {
	
	if(isset($_POST['delete_comment'])){
		
		$stmt = $link->prepare("DELETE FROM `contact_form` WHERE `contact_id` = ?");
		$stmt->bind_param("i", $contact_id);
		$contact_id = clean_input($_GET['contact_id']);
		$stmt->execute();
		$stmt->close();
		
		
	} 
}

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And this is what I want to appear once the function runs and the record is deleted:

	<script>
	swal(
  'Success!',
  'Message deleted.',
  'success'
)
	</script>

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To see what sweet alert is, go to :

https://limonte.github.io/sweetalert2/
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Most Valuable Expert 2011
Top Expert 2016

Commented:
OK, there are a few things to think about here.  

Sweet Alert looks susceptible to using JSON, and PHP can generate the JSON strings.  I haven't used it, but that seems like a good way to think about displaying custom messages from the PHP AJAX script.

The instructions appear to be out-of-order in the PHP function.  This is why we use error_reporting(E_ALL), so we can catch things that are amiss.  $contact_id is undefined in the bind_param() function call.

You might or might not care whether the DELETE query works.  If you care (and maybe want to adjust the Sweet Alert output) you would want to test the query for success or failure, and perhaps get the number of rows that were deleted.

Author

Commented:
Hi Ray,

My query is working fine and the delete works as it should. I used the W3 schools example as a base whereby they name their variables after they use bind_param. That's the only reason I defined $contact_id after the bind_param. You can check it out here:

http://www.w3schools.com/php/php_mysql_prepared_statements.asp

But, where should I put it then? Before I even start the $link->prepare()   ?

Oh, I was meant to put LIMIT 1 at the end of the SQL statement.. Will fix that on my end.
Most Valuable Expert 2011
Top Expert 2016
Commented:
Yeah, that part about naming variables after using them may be one of those things that works, but makes the computer science part of me itch.  If you're going to filter an external variable with something like this...
$contact_id = clean_input($_GET['contact_id']);

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... my instinct would be to put that before the bind statement.  I think most "linters" would flag an undefined variable.

I think your instincts are good about using AJAX.  The order of events is such that you will need a PHP server-side event to occur after the web page is loaded.  This article explains the HTTP request/response sequence.
https://www.experts-exchange.com/articles/11271/Understanding-Client-Server-Protocols-and-Web-Applications.html

If you're looking for some ideas around AJAX and JSON, this might be helpful.
https://www.experts-exchange.com/articles/22519/Understanding-JSON-in-PHP-and-JavaScript-Applications.html

Author

Commented:
Thanks for the tip Ray, I will do it before the bind statement from now.

I did a very basic course on ajax yesterday, so basic that it was only like an hour or something. I was hoping I could try use that knowledge but I think I need to learn some more about ajax and jquery. Anyway, I tried something like this but I get a blank screen as a result.

I think I will leave the ajax part out for now because I actually don't know enough to pull it off. I will have to do some more learning. I will give you points anyway since you advised me that I should be declaring my variables before binding.
Most Valuable Expert 2011
Top Expert 2016

Commented:
Here's the basics of jQuery and AJAX.  FWIW, it took me a long time to find any decent examples that showed the patterns from beginning to end.
https://www.experts-exchange.com/articles/10712/The-Hello-World-Exercise-with-jQuery-and-PHP.html

Cheers, ~Ray

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