Overtrue\Validation\Validator::addReplacers PHP Method

    public function addReplacers(array $replacers)
    {
        if ($replacers) {
            $keys = array_map('Overtrue\\Validation\\snake_case', array_keys($replacers));
            $replacers = array_combine($keys, array_values($replacers));
        }
        $this->replacers = array_merge($this->replacers, $replacers);
    }

 /**
  * Add the extensions to a validator instance.
  *
  * @param \Overtrue\Validation\Validator $validator
  */
 protected function addExtensions(Validator $validator)
 {
     $validator->addExtensions($this->extensions);
     // Next, we will add the implicit extensions, which are similar to the required
     // and accepted rule in that they are run even if the attributes is not in a
     // array of data that is given to a validator instances via instantiation.
     $implicit = $this->implicitExtensions;
     $validator->addImplicitExtensions($implicit);
     $validator->addReplacers($this->replacers);
     $validator->setFallbackMessages($this->fallbackMessages);
 }