PHP Form Validation Script

It is very essential to have the input to your form validated before taking the form submission data for further processing. When there are many fields in the form, the PHP validation script becomes too complex. Moreover, since you are doing the same or similar validation for most of the forms that you make, just too much of duplicate effort is spent on form validations.

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About this generic PHP form validation script

This generic PHP form validator script makes it very easy to add validations to your form.

We create and associate a set of "validation descriptors" with each element in the form. The "validation descriptor" is a string specifying the type of validation to be performed. For example, "req" means required, "alpha" means allow only alphabetic characters and so on.

Each field in the form can have zero, one or more validations. For example, the input should not be empty, should be less than 25 chars, should be alpha-numeric, etc

You can associate a set of validation descriptors for each input field in the form.

Download the PHP form validation script

You can download the PHP form validation script below:
php-form-validator.zip The zip file contains the form validation script formvalidator.php, documentation and usage samples.

Using the PHP form validation script

1. Include formvalidator.php in your form processing script

require_once "formvalidator.php"

2. Create a FormValidator object and add the form validation descriptors.

$validator = new FormValidator();
$validator->addValidation("Name","req","Please fill in Name");
$validator->addValidation("Email","email",
"The input for Email should be a valid email value");
$validator->addValidation("Email","req","Please fill in Email");

The first argument is the name of the input field in the form. The second argument is the validation descriptor that tells the type of the validation required. The third argument is the error message to be displayed if the validation fails.

3. Validate the form by calling ValidateForm() function

if(!$validator->ValidateForm())
{
    echo "<B>Validation Errors:</B>";
    $error_hash = $validator->GetErrors();
    foreach($error_hash as $inpname => $inp_err)
    {
        echo "<p>$inpname : $inp_err</p>\n";
    }
}

Example

The example below will make the idea clearer

<?PHP
require_once "formvalidator.php";
$show_form=true;
if(isset($_POST['Submit']))
{
    $validator = new FormValidator();
    $validator->addValidation("Name","req","Please fill in Name");
    $validator->addValidation("Email","email",
"The input for Email should be a valid email value");
    $validator->addValidation("Email","req","Please fill in Email");
    if($validator->ValidateForm())
    {
        echo "<h2>Validation Success!</h2>";
        $show_form=false;
    }
    else
    {
        echo "<B>Validation Errors:</B>";
        $error_hash = $validator->GetErrors();
        foreach($error_hash as $inpname => $inp_err)
        {
          echo "<p>$inpname : $inp_err</p>\n";
        }
    }
}
if(true == $show_form)
{
?>

<form name='test' method='POST' action='' accept-charset='UTF-8'>
Name: <input type='text' name='Name' size='20'>
Email: <input type='text' name='Email' size='20'>
<input type='submit' name='Submit' value='Submit'>
</form>

<?PHP
}//true == $show_form
?>

Adding Custom Validation

If you want to add a custom validation, which is not provided by the validation descriptors, you can do so. Here are the steps:

1. Create a class for the custom validation and override the DoValidate() function

class MyValidator extends CustomValidator
{
    function DoValidate(&$formars,&$error_hash)
    {
        if(stristr($formars['Comments'],'http://'))
        {
            $error_hash['Comments']="No URLs allowed in comments";
            return false;
        }
    return true;
    }
}

2. Add the custom validation object

$validator = new FormValidator();
$validator->addValidation("Name","req","Please fill in Name");
$validator->addValidation("Email","email",
 "The input for Email should be a valid email value");
$validator->addValidation("Email","req","Please fill in Email");
$custom_validator = new MyValidator();
$validator->AddCustomValidator($custom_validator);

The custom validation function will be called automatically after other validations.

Table of Validation Descriptors

Here is the list of all validation descriptors:

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