Undefined index: PHP checkbox

Question

The idea is to have list of checkbox for user to select genre type. The genre input is from database. Because the sql will return the result in an array, a for loop to get all the values and make them into a check box. The error come from third line in the loop. It show undefined index genre

<div class="list-group">
      <h3>Genre</h3>
      <?php
      $search_genre = "SELECT DISTINCT(genre) FROM movie_db WHERE product_status ='1' ORDER BY movieid DESC"
      $statement = mysqli_query($conn,$search_genre);
      $result = mysqli_fetch_all($statement);
      foreach ($result as $row){
         ?>
         <div class="list-group-item checkbox">
         <label><input type="checkbox" class="common_selector genre" value="<?php echo$row['genre'];?> > <?php echo $row['genre'];?></label>
</div>
<?php
}
?>

maybe its a type but you're missing a space after your echo . - echo$row['genre']; — Vladimir Mujakovic, Oct 21 '18 at 00:49
Are you sure your SQL call is returning the desired results? — symlink, Oct 21 '18 at 00:50
you are also missing a ; after youre $search_genre variable declaration — Vladimir Mujakovic, Oct 21 '18 at 00:51

ivanivan · Answer 1 · 2018-10-21T01:05:13.803

You need to give the checkbox a name, and since you are allowing multiple selections (checkbox vs radio button) you need to use a PHP array style name -

<label>
<input 
name="mycheckbox[]" 
type="checkbox" 
class="common_selector genre" 
value="<?php echo $row['genre'];?>"
<?php // here is where you could throw a check to make it pre-selected
by printing the word "checked" if a logical condition is met, etc ?>
> 
<?php echo $row['genre'];?> 
</label>

Now, in your processing script, you can reference $_POST['mycheckbox'] and it will contain an array with one or more values in it, one element per selected value.

for($i=0;$i<count($_POST['mycheckbox']);$i++){
  print("selected value $i: ".$_POST[['mycheckbox'][$i]."\n");
}

Edit -

Just for giggles, if you wanted only one single selection (radio button) you STILL name the elements the same thing, you just leave off the PHP array brackets []

<label>
<input 
name="myradio" 
type="radio" 
class="common_selector genre" 
value="<?php echo $row['genre'];?>"
<?php /* here is where you could throw a 
      check to make it pre-selected
      by printing the word "selected" 
      if a logical condition is met, etc 
      note in a series the last one selected
      stays selected if you print selected more than once
      */
?>
> 
<?php echo $row['genre'];?> 
</label>

And the selected radio group value is available as $_POST['myradio']

i changed it but still run into the same error. is it somethig related to the return value of $result? — user9510596, Oct 21 '18 at 02:22

Undefined index: PHP checkbox

1 Answers1