Making sure one input field is greater than the other in Laravel - php

Question

I have a form that has a start_odo and an end_odo for vehicle mileage tracking that user needs to enter. The problem is that currently, they can enter a start_odo that is higher than the end_odo and that results in a negative difference. Is any way to ensure that the end_odo will always have to be higher?
Being fairly new to Laravel, I read about the gt:field but I am not quite sure how to interpret it in my code as it looks different. Could someone nudge me in the right direction.
Controller:
public function store(Request $request)
{
// $energy = new Maintenance;
$energy = new VehicleLog();
$energy->start_odo = $request->input('start_odo');
$energy->end_odo = $request->input('end_odo');
$energy->km = $request->input('end_odo') - $request->input('start_odo');
$energy->save();
return redirect('/vmaintenance')->with('success', 'data added');
}
my view:
<div class="mb-3" style="float:left;" style="margin-left: 200px;">
<label for="recipient-name" style="width: 7em"class="col-form-label">Start ODO</label>
<input type="number"style="width: 7em" name="start_odo" class="form-control" id="recipient-name" min="0" required>
</div>
<div class="mb-3">
<label for="recipient-name" class="col-form-label">End ODO</label>
<input type="number" style="width: 7em" name="end_odo" class="form-control" id="recipient-name" min="0" required>
</div>
The validation code I saw while reading:
$request->validate([
'detail' => 'gt:20',
]);

Answer 1

you have to figure out yourself how to write code. there are lots of answers and tutorials out there regarding this. however i am adding this answer to get you started.
in your store method, validate the data before saving to database.
public function store(Request $request)
{
// validation logic
$request->validate([
'start_odo' => 'required',
'end_odo' => 'required|gt:start_odo',
]);
// if validation passes this will now store values in db
$energy = new VehicleLog();
$energy->start_odo = $request->input('start_odo');
$energy->end_odo = $request->input('end_odo');
$energy->km = $request->input('end_odo') - $request->input('start_odo');
$energy->save();
return redirect('/vmaintenance')->with('success', 'data added');
}
now explore the doc how to show validation errors in the form and other ways to validate data.

Answer 2

As #zahidhasanemon had already indicated. You can achieve it with customs rules. First step would be to define the new validation rule in your AppServiceProvider.
class AppServiceProvider extends ServiceProvider
{
public function boot()
{
Validator::extend('greater_than_field', function($attribute, $value, $parameters, $validator) {
$min_field = $parameters[0];
$data = $validator->getData();
$min_value = $data[$min_field];
return $value > $min_value;
});
Validator::replacer('greater_than_field', function($message, $attribute, $rule, $parameters) {
return str_replace(':field', $parameters[0], $message);
});
}
}
Then you can use this new validation rule in your controller like that:
$request->validate([
// other validations rules
'end_odo' => 'required|greater_than_field:start_odo',
]);