ipv4validator.php

<?php

class IpV4Validator
{
    private $_ip;

    public function __construct( $ipAddr ) {
      $this->_ip = $ipAddr;
    }

    public function validate() {
      // let's assume we have isValid() 
      if( false === $this->isValid() ) {
        throw new \InvalidArgumentException( $this->_ip . ' is not a valid IP v4 address' );
      }
    }

    public function isValid() {
      // logic to validate ip v4
      return true;
    }
}

?>