PHP multiple interfaces to implement validation functionality?

Question

I am trying to implement validation functionality on a website on which i am working.

I have created an interface entitled Validator which my classes then implement. The single function in my interface is validate($input).

Then I have a class e.g EmailValidator which now implements this. In its implementation of validate() it checks if the input is a valid email and returns true or false respectively.

Now.. I want to implement a check whereby two inputs are sent and I check if they are equal. For example in the case of passwords. As this interface function only takes one input it is not suitable.

I can create a second interface with a validate function which takes two inputs e.g PairValidator. Is this however the optimal way to implement what i want?

My concern arise because due to the possibility of validation functions i may need i could plausibly have loads of interfaces e.g SetValidator for checking if a value is in a set..

Thanks

You can make methods in the class that aren't declared in the interface. — Jordan Doyle
– Jordan Doyle, Commented May 21, 2013 at 15:13
I don't think interface implementation is the answer here. Consider just having a utility Validator class which has methods to validate different field types. — Sam Dufel
– Sam Dufel, Commented May 21, 2013 at 15:16
What you could do is just present the multiple value to validate to the validator as an array like $validator->validate(array("val1"=>"Test", "val2"=>"Test2"); — Orangepill
– Orangepill, Commented May 21, 2013 at 15:18
@Orangepill I think you read my comment wrong! That's what I said. — Jordan Doyle
– Jordan Doyle, Commented May 21, 2013 at 15:19

Orangepill · Accepted Answer · 2013-05-21 15:34:37Z

1

There are a couple of ways that you can go with this. A couple of easy ones to that won't break your current interface definition are:

1) Present what needs to be validated as an array.

$validator->validate($_POST["password"],$_POST["password_repeat"]);

2) construct the validator with one of the values that you need.

$validator = new ValidateEquals($_POST["password"]);
$validator->validate($_POST["password_repeat"]);

one way that you can do that would break your current interface and would require changing any validators you have now would be to remove the parameter altogether from the interface definition and use position parameters via func_get_args

interface Validator {
    public function validate();
}

class EqualsValidator implements Validator {
    public function validate(){
        $args = func_get_args();
        return $args[0] == $args[1];
    }
}

answered May 21, 2013 at 15:34

Orangepill

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5 Comments

Henrique Barcelos Over a year ago

IMO, the 2nd suggestion is the best one. This way, you don't need to mess up the interface every time the validation rules changes.

Orangepill Over a year ago

It all depends if the validators are used in a static sense then version two is out. Version 3 is the most flexible but you lose a lot of compile time checks.

Henrique Barcelos Over a year ago

What do you mean with "in a static sense"?

Orangepill Over a year ago

I mean instance where user would say EmailValidator::validate($email);

Henrique Barcelos Over a year ago

Well, that's why we maybe should not use static for this purpose. By using this, we now loose the capability of automate and chain validators. It could make sense, since validators usually do not have state, but we loose flexibility. And also, in this case, there would be no need for an interface.

bitWorking · Accepted Answer · 2013-05-21 15:38:01Z

0

I have solved the same problem with following interface method:

public function isValid($value, array $values = array());

$values has all form fields as associative array available. So you can work with these values if you need to.

My equal validator looks like:

class Equal implements IValidator
{
    private $_varname = null;

    public function __construct($varname)
    {
        $this->_varname = $varname;
    }

    public function isValid($value, array $values = array())
    {
        if (!array_key_exists($this->_varname, $values)) {
            // set error message
            return false;
        }

        $otherValue = $values[$this->_varname];

        if ($value != $otherValue) {
            // set error message
            return false;
        }
        return true;
    }
}

So I set the other form key to be checked in the constructor.

edited May 21, 2013 at 15:38

answered May 21, 2013 at 15:26

bitWorking

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2 Comments

Thomas Clowes Over a year ago

Interesting. And if i want to reuse the instance of the class simply add a setter method so I could change $_varname? Likewise for checking if a value is in a set are you proposing using exactly the same whereby you set the set array in the constructor and then validate against it in the function?

bitWorking Over a year ago

Yes..exactly, this is how my InArray validator works. If you like you can make a setter for the private fields but I had no needs to reuse an validator instance. And I don't like it because the interface make not much sense if you have methods that aren't declared in the interface.

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