O'Reilly

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

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

//initialize
$how_hear = count($_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.

O'Reilly Velocity Conference
Save 20% with discount code AFF20

Recent Features

  • Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • Create Namespaced Classes with MooTools

    MooTools has always gotten a bit of grief for not inherently using and standardizing namespaced-based JavaScript classes like the Dojo Toolkit does.  Many developers create their classes as globals which is generally frowned up.  I mostly disagree with that stance, but each to their own.  In any event,...

Incredible Demos

  • Create a Context Menu with Dojo and Dijit

    Context menus, used in the right type of web application, can be invaluable.  They provide shortcut methods to different functionality within the application and, with just a right click, they are readily available.  Dojo's Dijit frameworks provides an easy way to create stylish, flexible context...

  • Drag &#038; Drop Elements to the Trash with MooTools 1.2

    Everyone loves dragging garbage files from their desktop into their trash can. There's a certain amount of irony in doing something on your computer that you also do in real life. It's also a quick way to get rid of things. That's...

Discussion

  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.

    http://stackoverflow.com/questions/19282526/validation-of-fields-with-same-name-and-class-get-typeerror-e-validator-method

  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:

    //initialize
    $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';
    

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

Recently on David Walsh Blog

  • Prevent Chrome from Translating a Page

    A while back I shared my favorite Google Chrome extension:  Google Art Project.  I've enjoyed seeing beautiful art when I open a new tab -- it's brought genuine happiness to my day, however small that happiness may be.  About a week ago, however, the art presented had...

  • Create Any Type Of Website With These Multi-Purpose Themes

    We have selected what we believe are the very best multipurpose WordPress themes on the market today. Our list contains a number of best sellers, several newcomers that are proving to be highly popular, and a few themes that are ideal for creating the types of...

  • An Introduction to Static Site Generators

    Static site generators seem to have been becoming more and more popular recently, but they’re not one of those ephemeral novelty things that grow in popularity as quickly as they fall into oblivion shortly after. For over a decade, many different projects — 394 of...

  • Automated Tests for Visual Responsive Layouts

    Today it's all about testing. In 2015, many developers knows about TDD and I personally think that testing is one of the key for quality products. But what about testing in a Front-end environment? How do you guys write your tests for a responsive page or...

  • Getting Dicey With Flexbox

    What if you could build complex CSS layouts in minutes? Flexbox is a new CSS layout spec that makes it easy to construct dynamic layouts. With flexbox, vertical centering, same-height columns, reordering, and direction agnosticism are a piece of cake. There's a popular myth floating around that...