PHP - Is This A Good Design? (database Url Linkage)

$search = $_GET['search'];
$search = preg_replace("/[^A-Za-z0-9]/", " ", $search);
$search = $mysqli->real_escape_string($search);

I've always had an issue needing to write and maintain script to validate both client side and sever side so a while back I wrote a validation class whose primary purpose was:

I recently looked at the code and it is a train wreck.  I used a single class and had a bunch of protected functions where some would validate per a given rule and return the message upon error and others would sanitize.  For non-typical rules required by the specific application, I would extend the class and add them.  Some of these added rules required other resources such as an entities primary key, a PDO connection, etc.

While inheritance worked fine to add simple rules, it did not do so for the rules which needed other resources.  Also, even though I used "final" on my base class methods, I never liked this single class of many methods as I couldn't use the same name for a given rule and sanitize method (i.e. would rather use digit and digit instead of digit and int).

I am thinking of changing it to something like the following.  While this is definitely better, I question whether I should be using traditional classes to define my standard and custom rules.  Any recommendations?  Thanks

class Validator
{
    protected $options,
    $rules=[
        "digit"=>function($value, $prop, $name){
            return /*validate and return error string or null*/;
        },
        "minlength"=>"ect, etc"    
    ];

    public function __construct(string $json, \Closure ...$customRules=[]) {
        $this->options=json_decode($json);
        $this->rules=array_merge($this->rules, $customRules);
    }
}

class Application
{
    public function someMethod() {
        $pdo=$this->pdo;
        $applicationCustomRules=[
            'someCustomRule'=>function($value, $prop, $name) use ($pdo) {
                return /*validate and return error string or null*/;
            }
        ];
        $validator=new Validator($json, ...$applicationCustomRules);

        //Which can be used such as:
        $jQueryOptions=$validator->getJQueryOptions();
        $validator->validate($data);
        $validator->validateProperty('account', $account);
    }
}