What would make a good PHP validaton class? - php

Question

I would like to read about your opinions on what the best way to create a validation class is.
Below i pasted in my version, it's not really extensive yet, but is it the right approach so far?
I want every element which could appear in a form and which should be validated to have its own properties, in terms of string length for strings or file size for images or files in general (see below).
Also, is it better to declare these rules as nested arrays or should I put them in one big string, which would then be split up during the process?
mb_internal_encoding("UTF-8");
class Phrase {
//creates parts of sentences, not important
static function additive(array $limbs) {
return implode(' and ', array_filter([implode(', ', array_slice($limbs, 0, -1)), end($limbs)], 'strlen'));
}
}
class Text {
static function validate($item) {
$err = array();
$value = $_POST[$item] ?? $_GET[$item];
$criteria = FormProcess::$criteria[$item];
foreach($criteria as $critKey => $critVal) {
if($critKey === 'required' && empty($value)) {
$err[] = "is required";
} else if(!empty($value)) {
switch($critKey) {
case 'length':
if(is_array($critVal)) {
//min and max set
if(mb_strlen($value) < $critVal[0] || mb_strlen($value) > $critVal[1]) {
$this->err[] = "must contain between {$critVal[0]} and {$critVal[1]} characters";
}
} else {
//max set only
if(mb_strlen($value) > $critVal) {
$err[] = "must contain a maximum of $critVal characters";
}
}
break;
case 'pattern':
if(!preg_match($critVal[0], $value)) {
$err[] = "may consist of {$critVal[1]} only";
}
break;
case 'function':
$result = static::$critVal($value);
if($result) {
$err[] = $result;
}
break;
}
}
}
if(!empty($err)) {
return "{$criteria['name']} " . Phrase::additive($err) . "!";
}
return false;
}
private static function email($email) {
//checks if given string is a valid email address
if(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
return "is invalid";
}
return false;
}
}
class File {
//checks for aspects like filesize...
static function validate() {
//...
}
}
class Image extends File {
static function validate() {
parent::validate(); //perform general file checks first
//...checks for images specifically
}
}
class Video extends File {
static function validate() {
parent::validate(); //perform general file checks first
//...checks for videos specifically
}
}
class FormProcess {
public $errors;
//declare, what kind of requirements the items must meet
static $criteria = array(
'email' => array(
'type' => 'Text',
'required' => true,
'name' => 'Email',
'length' => 48,
'function' => 'email',
),
'username' => array(
'type' => 'Text',
'required' => true,
'name' => 'Username',
'length' => [4, 24],
'pattern' => ['/^[-\w]+$/', "alphanumeric characters, underscores and hyphens"],
),
'password' => array(
'type' => 'Text',
'required' => true,
'name' => 'Password',
'length' => [6, 100],
'pattern' => ['/^[\S]+$/', "non-whitespace characters"],
),
);
//runs the validate function on each item while storing occuring errors
function __construct(array $items) {
foreach($items as $item) {
$class = self::$criteria[$item]['type'];
$result = $class::validate($item);
if($result) {
$this->errors[] = $result;
}
}
}
}
Then all you had to do, is, naming all expected items (by their html 'name' attribute in the form) in an array and pass it through the constructor, which would then run the appropriate validation function on each item.
$expected = ['username', 'password'];
$signup = new FormProcess($expected);
if($signup->errors) {
?>
There was something wrong with your request:
<ul>
<?php foreach($signup->errors as $error) { ?>
<li><?= $error ?></li>
<?php } ?>
</ul>
<?php
}
I hope to learn from mistakes and make improvements to the code from you where they are needed.
Thank you in advance!