Open-ended Date Range Validation

open-ended-date-range.md

The Problem

Laravel 9, PHP 8.1. I had a form with two fields, start_date and end_date. These fields were nullable, so either could be left blank to set an pen-ended start or end of the date range.

The dates needed to be validated to ensure the end date was after the start date, and the start date was before the end date. But only when both are set. The problem with applying the before and after validation rules is that if the field being compared against is empty, then the validation rule always failed.

The Solution

What was needed was for these rules to be injected only if needed, i.e. conditionally. The when() rule achieves this, and this gist shows how.

    $rules = [
        // ...
        'start_date' => [
            'nullable',
            'date',
            \Illuminate\Validation\Rule::when(
                fn (\Illuminate\Support\Fluent $input) => $input->end_date ?? null,
                fn () => 'before:end_date',
           ),
        ],
        'end_date' => [
            'nullable',
            'date',
            \Illuminate\Validation\Rule::when(
                fn (\Illuminate\Support\Fluent $input) => $input->start_date ?? null,
                fn () => 'after:start_date',
            ),
        ],
    ];

This is the logic that will be applied:

start_date	end_date	start_date validation	end_date validation
null	null	valid	valid
any date	null	valid	valid
null	any date	valid	valid
low date	high date	valid	valid
high date	low date	invalid	invalid

I wanted to put the same validation on both start and end dates, so that if there is a validation error (the dates are in the wrong order) then both related form fields are highlighted with the appropriate error message.