Custom Laravel validation messages

Laravel 5.7.*

Also You can try something like this. For me is the easiest way to make custom messages in methods when you want to validate requests:

public function store()
{
    request()->validate([
        'file' => 'required',
        'type' => 'required'
    ],
    [
        'file.required' => 'You have to choose the file!',
        'type.required' => 'You have to choose type of the file!'
    ]);
}

If you use $this->validate() simplest one, then you should write code something like this..

$rules = [
        'name' => 'required',
        'email' => 'required|email',
        'message' => 'required|max:250',
    ];

    $customMessages = [
        'required' => 'The :attribute field is required.'
    ];

    $this->validate($request, $rules, $customMessages);

You can provide custom message like :

$rules = array(
            'URL' => 'required|url'
        );    
$messages = array(
                'URL.required' => 'URL is required.'
            );
$validator = Validator::make( $request->all(), $rules, $messages );

if ( $validator->fails() ) 
{
    return [
        'success' => 0, 
        'message' => $validator->errors()->first()
    ];
}

or

The way you have tried, you missed Validator::replacer(), to replace the :variable

Validator::replacer('custom_validation_rule', function($message, $attribute, $rule, $parameters){
    return str_replace(':foo', $parameters[0], $message);
});

You can read more from here and replacer from here

For Laravel 8.x, 7.x, 6.x
With the custom rule defined, you might use it in your controller validation like so :

$validatedData = $request->validate([
       'f_name' => 'required|min:8',
       'l_name' => 'required',
   ],
   [
    'f_name.required'=> 'Your First Name is Required', // custom message
    'f_name.min'=> 'First Name Should be Minimum of 8 Character', // custom message
    'l_name.required'=> 'Your Last Name is Required' // custom message
   ]
);

For localization you can use :

['f_name.required'=> trans('user.your first name is required'],

Hope this helps...