How do I dynamically append something to a variable in PHP? - php

Question

I have a form like so:
<?php if (isset($_POST['artist'])) {
// do something
} ?>
<form name="admin_on_artist_<?php echo $artist->ID; ?>" action="" method="POST">
<p class="artist-negative">
<label for="artist"><input type="checkbox" name="artist_<?php echo $artist->ID; ?>" id="artist_<?php echo $artist->ID; ?>"> Check this?</label>
</p>
<button type="submit">Update</button>
</form>
On the page in question, this form is shown many times in a foreach loop. However, when I submit any given form, it updates all of the forms, which is not what I want.
How can I append the $artist->ID to $_POST['artist'] so that I get something like:
$_POST['artist_1'] to match the checkbox attributes?

Answer 1

You could pair your foreach that generates the frontend form markup with a foreach that processes the form submission. Something like:
<?php
$regex = '/^artist_([0-9]+)$/'
foreach (array_keys($_POST) as $key) {
if (preg_match($regex,$key,$matches)) {
$artistId = (int)$matches[1];
// do something with $_POST[$key] according to $artistId
}
}
This works for a single field submission or a multiple field submission.
Alternatively, you could do something on the frontend in JS (as #smith suggests in the comments) to ensure the form submission always has the same, well-known keys, populating a hidden form with the current submission. With this approach you would have to add another field to the form that contains the ID.

Answer 2

The solution for this was much simpler than I was able to grasp at first, but basically I just had to do this, the key difference between this and my original question being the first two lines:
<?php $artist_form_id = 'artist_'.$artist->ID;
if (isset($_POST[$artist_form_id])) {
// do something
} ?>
<form name="admin_on_artist_<?php echo $artist->ID; ?>" action="" method="POST">
<p class="artist-negative">
<label for="artist"><input type="checkbox" name="artist_<?php echo $artist->ID; ?>" id="artist_<?php echo $artist->ID; ?>"> Check this?</label>
</p>
<button type="submit">Update</button>
</form>