A little bit functional

MobileValidator.php

<?php

namespace App\Validators;

class MobileValidator
{

    public function validate($attribute, $number, $countries)
    {
        try {
            $number = (int)$number;
            foreach ($countries as $country) {
                $func_name = 'is' . ucfirst($country) . 'Mobile';
                $bool = call_user_func([$this, $func_name], $number);
                if ($bool) {
                    return $number;
                }
            }
            return false;
        } catch (MethodNotFoundException $e) {
            throw new Exception($e);
        }
    }

    private function isTWMobile($number)
    {
        $is_mobile_func = $this->isMobileFunc(9, 9);
        return $is_mobile_func($number);
    }

    private function isHKMobile($number)
    {
        $mobile_prefix_numbers = [5, 6, 9];
        $is_mobile_func = $this->isMobileFunc(8, $mobile_prefix_numbers);
        return $is_mobile_func($number);
    }

    private function isMacauMobile($number)
    {
        $is_mobile_func = $this->isMobileFunc(8, 6);
        return $is_mobile_func($number);
    }

    private function isMobileFunc($number_length, $number_prefix)
    {

        if (is_array($number_prefix)) {
            $is_prefix_func = $this->isPrefixByArrayFunc($number_prefix);
        } else {
            $is_prefix_func = $this->isPrefixByIntFunc($number_prefix);
        }

        return function($number) use ($number_length, $is_prefix_func) {
            if (strlen($number) === $number_length && $is_prefix_func($number)) {
                return true;
            } else {
                return false;
            }
        };
    }

    private function isPrefixByArrayFunc($number_prefix)
    {
        return function($number) use ($number_prefix) {
            return in_array(substr($number, 0, 1), $number_prefix);
        };
    }

    private function isPrefixByIntFunc($number_prefix)
    {
        return function($number) use ($number_prefix) {
            return (int)substr($number, 0, 1) === $number_prefix;
        };
    }

}