Update a value in a table using checkbox in PHP - php

Question

I'm a beginner in php and I have a problem regarding checkbox.
First thing is that, in the form I don't know if name=medID[] is specifically used as an array. or a normal string like medID will work? and how exactly is it useful to use an array.?
When I'm updating the value in query both $quan and $medID values are not passing in the query.
In browser it shows "Alloted Succesfully" but the database value of quantity is not changing. when i replace $quan and $imp value to some integers then it works fine.
<tbody>
<tr>
<form method="post" action="ytube.php?array=hospitalstock&hospitalID=<?php echo $opened['hospitalID']; ?>&id=allot" role="form">
<div class="form-group">
<td class="vcenter"><input type="checkbox" name="medID[]" id="check" value="<?php echo $list['medID']; ?>" /></td>
</div>
<td><?php echo $list['item'] ?> </td>
<td><?php echo $list['price'] ?> </td>
<td><?php echo $list['quantity'] ?> </td>
<td><?php echo $list['subtotal'] ?> </td>
<div class="form-group">
<td><input type="text" name="quantity" id="quantity" class="form-control" /> </td>
</div>
</tr>
<?php }} ?>
<div class="form-group">
<input class="submit" type="submit" value="Allot Medicine" name="submit" class="form-control" />
</div>
</form>
</tbody>
</table>
<?php
$id=$_POST['medID'];
$quan=$_POST['quantity'];
if(isset($_POST['submit'])){
if(empty($id) || $id==0){
echo 'Select medicines to allot ';
}else{
echo $quan;
$imp= implode(", ",$id);
$q="UPDATE hospitalstock SET quantity= (quantity - '.$quan.') WHERE medID IN('.$imp.')" ;
$r=mysqli_query($conn, $q);
if(isset($r)){
echo 'Alloted Succesfully';
}
}
}
?>

Answer 1

Yes a normal string like madID will work just aswell.
name="medID" => $_post['medID']
name="medID[]" => $_post['medID'][0] de last [0] will get you the first element of the array
An array could be really helpful when it's a dynamically created form. A form where the number of inputs is not set, for example a contact form where you can click on a plus icon to add another text input for multiple phone numbers. Bacause its unknown how many phone numbers someone have its easier to just retrieve one variable as an array and iterate over this array after.
Don't you get an error like:
Notice: Undefined index: medID in ....
In your code you have name="medID[]" and $_post['medID']. So your form is sending an array but you retrive a normal variable. Just delete [] from name="medID[]"
Because of that if(empty($id) $id will always be empty so you don't even reach your query.

Answer 2

Few things to say; first I don't understand the concept of using a query string for action when you are using post as a method for submitting the values. Secondly if you are trying to consume the values from the query string as well; then I can't find the $_GET[] in your entire program. Third is a suggestion to use $_REQUEST[] when you are not sure about the get or post collections. Also, the name="medID[]" won't create any array for PHP. Is the ytube.php the same page where you have created this form?