Using Form Input Arrays For Checkboxes

By  on  

One way that I've gotten faster at XHTML forms is using input arrays whenever possible. Input arrays allow me to deal with just one variable for checkboxes that serve as multiple answers to one question. Here's how the process works.

Step 1: The XHTML Form

<table cellpadding="0" cellspacing="2">
		<td><input type="checkbox" name="how_hear[]" id="how_hear1" value="Website" <?php echo in_array('Website',$how_hear) ? 'checked="checked"' : ''; ?> /></td>
		<td style="padding-left:3px"><label for="how_hear1">Website</label></td>
		<td><input type="checkbox" name="how_hear[]" id="how_hear2" value="TV Commercial" <?php echo in_array('TV Commercial',$how_hear) ? 'checked="checked"' : ''; ?> /></td>
		<td style="padding-left:3px"><label for="how_hear2">TV Commercial</label></td>
		<td><input type="checkbox" name="how_hear[]" id="how_hear3" value="Magazine Ad" <?php echo in_array('Magazine Ad',$how_hear) ? 'checked="checked"' : ''; ?> /></td>
		<td style="padding-left:3px"><label for="how_hear3">Magazine Ad</label></td>
		<td><input type="checkbox" name="how_hear[]" id="how_hear4" value="Billboard" <?php echo in_array('Billboard',$how_hear) ? 'checked="checked"' : ''; ?> /></td>
		<td style="padding-left:3px"><label for="how_hear4">Billboard</label></td>
		<td><input type="checkbox" name="how_hear[]" id="how_hear5" value="Other" <?php echo in_array('Other',$how_hear) ? 'checked="checked"' : ''; ?> /></td>
		<td style="padding-left:3px"><label for="how_hear5">Other</label></td>

Note that the name attribute of each input is the same: how_hear[]. The brackets indicate that the input field is an array. Also note the PHP in each input tag that determines if the chechbox should checked initially.

Step 2: The PHP Form Validation and Processing

$how_hear = count($_POST['how_hear']) ? $_POST['how_hear'] : array();

//echo out their choices separated by a comma
echo count($how_hear) ? implode(', ',$how_hear) : 'Nothing';

To avoid PHP warnings, we declare the $how_hear array at the very top.

PHP's count() function returns the number of items selected, so we you require at least one be checked, count() is what we'll use.

Lastly, to display the selections as a list, we use the implode() function.

That's it! Click here to see an example.

Recent Features

  • By
    I&#8217;m an Impostor

    This is the hardest thing I've ever had to write, much less admit to myself.  I've written resignation letters from jobs I've loved, I've ended relationships, I've failed at a host of tasks, and let myself down in my life.  All of those feelings were very...

  • By
    Convert XML to JSON with JavaScript

    If you follow me on Twitter, you know that I've been working on a super top secret mobile application using Appcelerator Titanium.  The experience has been great:  using JavaScript to create easy to write, easy to test, native mobile apps has been fun.  My...

Incredible Demos

  • By
    iPhone Checkboxes Using MooTools

    One of the sweet user interface enhancements provided by Apple's iPhone is their checkbox-slider functionality. Thomas Reynolds recently released a jQuery plugin that allows you to make your checkboxes look like iPhone sliders. Here's how to implement that functionality using the beloved...

  • By
    Digg-Style Dynamic Share Widget Using MooTools

    I've always seen Digg as a very progressive website. Digg uses experimental, ajaxified methods for comments and mission-critical functions. One nice touch Digg has added to their website is their hover share widget. Here's how to implement that functionality on your site...


  1. I didn’t test yet but makes sense… It surely will help retrieving data from checkboxes (what was always trouble)…

    And I’m amazed how often you publish articles Dave, congrats =) I’m very happy I could find your blog and it’s been very helpful!

  2. Great tips !
    I use this method for “Delete” :

    for ($i = 0; $i < count($_POST['delete']); $i++) {
    $requete = mysql_query("DELETE FROM table
    WHERE id='".$_POST['delete'][$i]."'");
  3. Catar4x OUCH! you know that this is vulnerable to sql injection? Never put request params into sql like that without escaping them for ‘, ; and ” otherwise someone could create a form which would post this.. 1′;drop table; select * from table where id=’
    mysql would execute three statements…

    DELETE FROM table WHERE id=’1′;

    drop table table;

    select * from table where id=$_POST[‘delete’][$i]

  4. didier

    how about xhtml validation?
    I’ve been using the [ ] brakets to pass arrays to php but this won’t validate as xhtml.

  5. Was quite simple, but this article saved a day of repeated stupid mistakes, thank you.

  6. dwargo

    name=”how_hear[]”… I’m in shock… How didn’t I know this?

    Thank you, you just saved me rewriting my class from scratch!

  7. It is called a ternary operator it is short hand for an if statement
    (if this is true)? do this : else do this

  8. pim

    @didier this is not true, the square brackets validate perfectly (I just checked). XHTML expects inputs to be enclosed in a fieldset tag though.

  9. Daniel

    Does this array technique work with other types of inputs as well?

  10. Nsaji

    it works with other inputs as well. i just tried it

  11. Staffan

    Is it possible to make the echo to INPUT INTO a table instead?
    I just don’t understand how.

    I want the fields to end up in a table on separate lines instead.
    So, that how_hear is in a table where I will also have the user.
    So on each line I want the how_hear and next to that the user_id.
    If they check more than one checkbox, I want it to add those fields as separate inputs.

    Since I am planning to use it as genre for music. So the user can check more than one genre for a song.

  12. rafaCode

    Do not use this technique if what you expect at any point, to be able to use jquery validation on your fields.

  13. mdla

    Thank You veeeeeeeeeery much! You saved my life! I was looking the way to get the values of my selected checkboxes for about 2 days. It works perfectly for me in Laravel with the corresponding changes.
    If someone else need it, check the code below:

    $how_hear = count(Input::has('how_hear')) ? Input::get('how_hear'): array();
    //pass the var that contain the choices separated by a comma, to the Blade Template as correspond.
    $checkboxes= count($how_hear) ? implode(', ',$how_hear) : 'Nothing';
  14. Mladen

    Is this option added in html5?

Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!