Treehouse

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.

ydkjs-5.png

Recent Features

  • 5 More HTML5 APIs You DidnâÄôt Know&nbsp;Existed

    The HTML5 revolution has provided us some awesome JavaScript and HTML APIs.  Some are APIs we knew we've needed for years, others are cutting edge mobile and desktop helpers.  Regardless of API strength or purpose, anything to help us...

  • CSS&nbsp;@supports

    Feature detection via JavaScript is a client side best practice and for all the right reasons, but unfortunately that same functionality hasn't been available within CSS.  What we end up doing is repeating the same properties multiple times with each...

  • Create Namespaced Classes with&nbsp;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...

Incredible Demos

  • CSS&nbsp;Filters

    CSS filter support recently landed within WebKit nightlies. CSS filters provide a method for modifying the rendering of a basic DOM element, image, or video. CSS filters allow for blurring, warping, and modifying the color...

  • MooTools TextOverlap&nbsp;Plugin

    Developers everywhere seem to be looking for different ways to make use of JavaScript libraries. Some creations are extremely practical, others aren't. This one may be more on the "aren't" side but used correctly, my TextOverlap plugin...

  • Introducing MooTools&nbsp;ScrollSide

    This post is a proof of concept post -- the functionality is yet to be perfected. Picture this: you've found yourself on a website that uses horizontal scrolling instead of vertical scrolling. It's an artistic site so you accept that...

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=‚Äô1′;

    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. […] Using Form Input Arrays For Checkboxes […]

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

Use Code Editor