Formidable, the pragmatic forms library

v2.2.1 2023-10-06 16:22 UTC


PHP 7 PHP 7.1 PHP 7.2 Build status paypal

Formidable is a PHP library to handle forms. It parses an HTML form and allows you to manipulate it from your PHP code, and then render it.

How does it work?

Step 1: Download & install Formidable

Via composer:

    "require": {
        "gregwar/formidable": "dev-master"

Or with a clone of the repository:

git clone

Or downloading it:

Step 2: Write your form in HTML

First, you have to write your code in HTML, for instance:

<!-- forms/example.html -->
<form method="post">
    Enter your name: 
    <input type="text" name="name" /><br />
    <input type="submit" />

Step 3: Give it to Formidable

In your PHP code, give your form to Formidable:


// Formidable will parse the form and use it to check integrity
// on the server-side
$form = new Gregwar\Formidable\Form('forms/example.html');

$form->handle(function() {
    echo "Form OK!";
}, function($errors) {
    echo "Errors: <br/>";
    foreach ($errors as $error) {
        echo "$error<br />";

echo $form;

Simple, right?

Step 4: Enjoy the magic

You can then use the Formidable API to play with your form:


// Will set the value of the field
$form->name = "Bob";

// Will get the value of the field
$name = $form->name;

// Adds a constraint on the name
$form->addConstraint('name', function($value) {
    if (strlen($value) < 10) {
        return 'Your name should be at least 10 characters!';

// Adds a constraint on the whole form
$form->addConstraint(function($form) {
    if ($form->getValue('pass1') != $form->getValue('pass2')) {
        return 'The passwords are different';

You can also try to change your form and add constraint directly in the HTML code:

<input type="text" name="name" minlength="10" />

This will force the text to be at least 10 characters long when the server-side constraints will be checked.

Want a CAPTCHA to secure your form?

<input type="captcha" name="code" />

This will generate an image and an input field on the client-side, and use session on the server-side to check that the code is correct.

Note that this will use the dependency with Gregwar/Captcha library (you will have to install dependencies using composer).


The following input types are supported:

  • input tags, with types:
    • text
    • number or numeric, see min and max attributes
    • int or integer, see min and max attributes
    • file
    • checkbox
    • radio
    • hidden
    • password
    • captcha, will automatically generate an image
    • date, will generate three selects, and return a DateTime as data
    • multiradio and multicheckbox (see the source section)
  • textarea
  • select


Note that some attributes are not HTML-valid, like maxlength:

<input type="text" name="name" maxlength="10" />

It will not be rendered in the HTML form, but will be used to check integrity.

Here is the list of available attributes:

  • minlength: the minimum length of the value
  • maxlength: the maximum length of the value
  • regex: the regexp that the value should respect
  • min (for numbers): the minimum value
  • max (for numbers): the maximum value
  • required: tell that the field is required
  • readonly: the field is readonly and should not be modifier
  • value: the default value for the field
  • min-entries: specify the minimum number of entries that you should provide for a multiple (see below)
  • max-entries: specify the maximum number of entries that you can provide for a multiple (see below)
  • entries: specify both minimum and maximum number of entries for a multiple (see below)


You can call these method on your $form object:

  • posted(): return true if the form was posted
  • check(): check the form and return an array of validity errors
  • handle($callback, $errorCallback), this shortcut method call posted and check(), and will call $callback if the form is valid, $errorCallback else
  • setAttribute($field, $attr, $value): sets an extra attribute on a field
  • getAttribute($field, $attr): gets an extra attribute on a field
  • source($source, $values): feed a source (see the "Source" section)
  • setPlaceholder($name, $value): sets a placeholder value (see below)
  • addConstraint($field, $callback): adds a custom constraint on a field, the callback will be called with the field value and should return false if no problem, or an error string. If you just pass a closure to it, the closure will be called with the form passed as argument and can then do some tests involving multiple fields or form information.
  • setValue($field, $value): set the value of a field
  • getValue($field): gets the value of a field
  • setValues(array $values): set the values for some fields
  • getValues(): get the values of all fields

CSRF protection

An additional CSRF token is automatically inserted in the form and checked when it's submitted. Thus, all your forms will be secured.

The presence and validity of CSRF token is used to check that a form was posted when calling posted method (it's used internally in handle)

If you specify the name attribute in the form, the CSRF token will be different for this specific form, this will allow Formidable to make the difference of which form is submitted if there is multiple form on the same page.


The language for the errors can be set with setLanguage():


// Will set the language to french for errors
$form->setLanguage(new Gregwar\Formidable\Language\French);

Check that your language is supported in the Language directory, don't hesitate to participate!


You can use the sourcing system to populate dynamically a select, a multiradio or a multicheckbox:

<input type="multicheckbox" name="colours" source="colours" />

Then populate it with source:

$form->source('colours', array('red', 'yellow', 'blue'));

This will be rendered by some checkboxes.

You can do it this way with select:

<select name="colour">
    <options source="colours" />
    <option value="other">Other</option>

And then source it with the same method

Creating form from string

You can create form from a file or from a string, this will be detected automatically:


$form = new Gregwar\Formidable\Form('<form method="post">
    <select name="colour">
        <option value="blue">Blue</option>
        <option selected value="red">Red</option>
        <option value="green">Green</option>

echo $form->getValue('colour') . "\n";
// red

// Sets the color to blue
$form->setValue('colour', 'blue');

echo $form;
/* Will display:
<form method="post">
    <select name="colour" >
        <option selected="selected" value="blue">Blue</option>
        <option value="red">Red</option>
        <option value="green">Green</option>
    <input type="hidden" name="posted_token" value="d293dc38017381b6086ff1a856c1e8fe43738c60" />


You can also use mapping attribute to populate your form or to get back the form data in an array or in an object, for instance:


class Person
    protected $name;
    public function getName() { return $this->name; }
    public function setName($name) {
        $this->name = $name;

$person = new Person;

$form = new Gregwar\Formidable\Form('<form method="post">
    <input type="text" name="name" mapping="name" />


echo $form;
Will output something like:

<form method="post">
    <input required="required" type="text" name="name" value="Jack" />
    <input type="hidden" name="posted_token" value="aa27f437cc6127c244db14361fd614af51c79aac" />

Note that the mapping uses the Symfony PropertyAccessor, you can then use accessor as in the example above to populate properties.

You can use:

  • getData($entity = array()): populate and return entity with data populated
  • setData($entity): populate the form with the entity attributes

Creating multiple sub-forms

You can add multiple sub-forms to a page using the <multiple> tag:

<form method="post">
    Film name: <input type="text" name="film_name" mapping="name" />

    <multiple name="actors" mapping="actors">
        First name: <input name="first_name" mapping="firstName" /><br />
        Last name: <input name="last_name" mapping="lastName" /><br />
    <input type="submit" />

With this, the <multiple> can be used exactly like a field, but it will contains an array of elements.

Some JS will be injected in the page and allow you to add/remove some elements.

You can use min-entries and max-entries constraint to set limits on the number of entries in a multiple.

If you specify the same value for min-entries and max-entries, or specify a value for entries (which is actually an alias to do it), the number ofr inputs will be fixed and no javascript will be required.

Adding dynamic data into the form

In some case, you'll want to add custom data into the form, there is two way to do this.

First way: using the placeholders

The {{ something }} syntax allow you to simply inject data from the code, like this:


$form = new Gregwar\Formidable\Form('<form method="post">
    Hello {{ name }}!

$form->setPlaceholder('name', 'Bob');

echo $form;

In the example above, the {{ name }} will be rendered as Bob.

Note that placeholders may be used anyway excepted in the <form> and input tags:


$form = new Gregwar\Formidable\Form('<form method="post">
    <span style="color:{{ color }}">Hello</span>

$form->setPlaceholder('color', 'red');

echo $form;

Second way: using PHP form

You can also write your form using PHP, like a template, for instance:

    <?php echo $label; ?>: <input type="text" name="name" />
    <input type="submit" />

And then instanciate your form passing the template variables as a second argument:


$form = new Gregwar\Formidable\Form('the-above-form.php', array('label' => 'Your name'));

The $label will be interpreted using PHP.


For performances reasons, you may want to cache the parsed forms.

To do this, simply pass true as the third argument of the constructor:


 * Parsed data for the form will be serialized and stored in a cache file,
 * if you use this form often, this will offer you better performances.
$form = new Gregwar\Formidable\Form('form.html', null, true);

This will use the Gregwar/Cache system, you will need to get the composer dependencies of this repository or install it manually. By default, cache files will be wrote in the cache directory from where the script is run.

Try to run the performances.php script in the examples/ directory, this will give you an example of performance gain with cache.

You can also pass an instance of Gregwar\Cache\Cache as the third parameter, which will allow you to set the cache directory.


Gregwar\Formidable is under MIT License, have a look at the LICENSE file for more information.


V2.0.0 End support for PHP <5.6

V2.1.0 Remove hard dependency on Captcha library