Laravel 4自定义验证错误消息

so I was trying to add a custom validation rules like this:

public function validateDateAfterField($attribute, $value, $params)
{
  return strtotime($value) > strtotime($this->data[$params[0]]);
}

It takes the value and validate with another field in array of data being validate

I wanted it to produce an error message like this:

Event End Date must be a date after Event Start Date

Here is my custom validation message:

":attribute must be a date after :before"

I've added these custom validation attributes:

'attributes' => array(
        'event_start'=>'Event Start Date',
        'event_end' => 'Event End Date',
    )

But when I cannot access it in my custom validation class, I've tried something like this:

return str_ireplace(":before", $this->attributes[$parameters[0]], $message);

but got an error Undefined property:CustomerValidator::attributes

Anyone knows how to do this properly?

Edit:

Extended it in my global.php

Validator::extend('date_after_field', 'CustomValidator@DateAfterField');
Validator::resolver(function($translator, $data, $rules, $messages)
{
    return new CustomValidator($translator, $data, $rules, $messages);
});