post value of checkbox is empty - php

Question

I am trying to get checked values in unos.php file. I get empty post but could not figure it out where is mistake.
I want to check just one checkbox and according to post value received I will perform results.
<form method="post" action="unos.php">
<button type="submit" class="btn btn-primary" name="izmjena">Izmjena</button>
<table>
<thead>
<tr>
<th data-field="artikal" data-checkbox="true" > </th>
<th data-field="id" data-sortable="true">Id</th>
<th data-field="sifra" data-sortable="true">Sifra</th>
<th data-field="name" data-sortable="true">Naziv</th>
<th data-field="mjera" data-sortable="true">Jed. mjere</th>
<th data-field="stanjesa" data-sortable="true">Stanje Sa</th>
<th data-field="stanjebl" data-sortable="true">Stanje BL</th>
<th data-field="minkolicina" data-sortable="true">Min kolicina</th>
<th data-field="kategorija" data-sortable="true">Kategorija</th>
<th data-field="status" data-sortable="true">Status</th>
<th data-field="print" data-sortable="true">P</th>
</tr>
</thead>
<tbody>
<?php while ($r = $q->fetch()): ?>
<tr>
<td><input type="checkbox" name="artikli" value="<?.$r['ArtId'].?>"></td>
<td><?=$r['ArtId'] ?></td>
<td><?=$r['ArtSifra'] ?></td>
<td><?=$r['ArtNaziv'] ?></td>
<td><?=$r['JmNaziv'] ?></td>
<td><?=$r['ArtStanje']?></td>
<td><?=$r['ArtStanjeMo'] ?></td>
<td><?=$r['ArtMinKolic'] ?></td>
<td><?=$r['KatNaziv'] ?></td>
<td><?=$r['ArtAktivan'] ?></td>
<td><a onClick="window.open('kartica-artikla.php?id= <?=$r['ArtKategorija']?>','Websoft','width=800,height=500,left=0,top=100,screenX=0,screenY=100,menubar=yes,scrollbars=yes')" href "">
<img src="../../img/kartica.png" width="20"></td>
</tr>
<?php endwhile; ?>
</tbody>
<tfoot>
</tfoot>
</table>
file unos.php.. In this file I want to post value of checkbox
<?php
if (isset($_POST["izmjena"])) {
$id=$_POST["artikli"];
echo $id;
var_dump($id);
}
else{
}

Answer 1

Change:
<td><input type="checkbox" name="artikli" value="<?.$r['ArtId'].?>"></td>
To:
<td><input type="checkbox" name="artikli" value="<?php echo $r['ArtId']; ?>"></td>
Dont forget to close your form either :)

Answer 2

If you're using several checkboxes, you should be using an input checkbox with the following "name": "artikli[]".
The "[]" will send an array of values instead of sending a string.
Code:
<input type="checkbox" name="artikli[]" value="<?.$r['ArtId'].?>" />

Answer 3

checkbox's value will be present if it is checked. Do this -
$id=(!empty($_POST["artikli"])) ? $_POST["artikli"] : false;
and you are not echoing the whole html so no need to concate. Change -
<td><input type="checkbox" name="artikli" value="<? echo $r['ArtId'];?>"></td>