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.

The generic PHP form validator 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 0, 1, 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.

1. Include formvalidator.php in your form processing script
pre class="sh_php"> 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";
    }        
}	

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
?>

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.

req	The field should not be empty
maxlen=???	checks the length entered data to the maximum. For example, if the maximum size permitted is 25, give the validation descriptor as "maxlen=25"
minlen=???	checks the length of the entered string to the required minimum. example "minlen=5"
alnum	Check the data if it contains any other characters other than alphabetic or numeric characters
alnum_s	Allows only alphabetic, numeric and space characters
num	Check numeric data
alpha	Check alphabetic data.
alpha_s	Check alphabetic data and allow spaces.
email	The field is an email field and verify the validity of the data.
lt=??? lessthan=???	Verify the data to be less than the value passed. Valid only for numeric fields. example: if the value should be less than 1000 give validation description as "lt=1000"
gt=??? greaterthan=???	Verify the data to be greater than the value passed. Valid only for numeric fields. example: if the value should be greater than 10 give validation description as "gt=10"
regexp=???	Check with a regular expression the value should match the regular expression. example: "regexp=^[A-Za-z]{1,20}$" allow up to 20 alphabetic characters.
dontselect=??	This validation descriptor is for select input items (lists) Normally, the select list boxes will have one item saying 'Select One' or some thing like that. The user should select an option other than this option. If the index of this option is 0, the validation description should be "dontselect=0"
dontselectchk	This validation descriptor iss for check boxes. The user should not select the given check box. Provide the value of the check box instead of ?? For example, dontselectchk=on
shouldselchk	This validation descriptor is for check boxes. The user should select the given check box. Provide the value of the check box instead of ?? For example, shouldselchk=on
dontselectradio	This validation descriptor iss for radio buttons. The user should not select the given radio button. Provide the value of the radio button instead of ?? For example, dontselectradio=NO
selectradio	This validation descriptor is for radio buttons. The user should select the given radio button. Provide the value of the radio button instead of ?? For example, selectradio=yes
selmin=??	Select atleast n number of check boxes from a check box group. For example selmin=3
selmin=??	Select atleast n number of check boxes from a check box group. For example: selmin=3
eqelmnt=???	compare two elements in the form and make sure the values are the same For example, 'password' and 'confirm password'. Replace the ??? with the name of the other input element. For example: eqelmnt=confirm_pwd