How to Show Error Message with Dynamic Value in Laravel Array Validation

Laravel is a powerful PHP framework that simplifies various tasks in web development, including form validation. One common use case is handling array validation with custom error messages, especially when you need to display dynamic values within the error message. In this article, we'll go through a step-by-step guide on how to implement dynamic error messages in Laravel's array validation.

Prerequisites

Before we dive into the solution, make sure you have:

• A working Laravel environment (Laravel 8 or above)
• Basic knowledge of form validation in Laravel
• Composer installed on your system

Step 1: Understanding Array Validation in Laravel

Laravel's validation system is highly flexible. When validating arrays, you can use dot notation to specify rules for specific keys in the array.

For example, suppose you want to validate an array of emails:

$validated = $request->validate([
    'emails.*' => 'required|email'
]);

This rule ensures that every item in the emails array is a valid email address.

Step 2: Setting Up Dynamic Error Messages

It's often necessary to show which array item failed validation when validating arrays. Laravel provides a convenient way to generate dynamic error messages by using the :attribute placeholder in the custom error messages.

Let's modify our validation rules to use a dynamic error message.

Example Scenario:

Imagine a scenario where you are validating an array of products with attributes like name, price, and quantity. Here's how you can add custom error messages with dynamic values.

Step 3: Writing Validation Rules in the Controller

public function store(Request $request)
{
    $validated = $request->validate([
        'products.*.name' => 'required|string|max:255',
        'products.*.price' => 'required|numeric|min:0',
        'products.*.quantity' => 'required|integer|min:1',
    ], $this->customMessages());
    
    // Proceed with storing data after validation passes
}

Step 4: Creating Custom Error Messages

Next, define custom error messages for the array validation in the customMessages() method. You can include dynamic values such as the array index to provide more context about which array item caused the validation error.

protected function customMessages()
{
    return [
        'products.*.name.required' => 'The product name at position :position is required.',
        'products.*.price.required' => 'The product price at position :position is required.',
        'products.*.quantity.required' => 'The product quantity at position :position is required.',
    ];
}

Step 5: Replacing Placeholder with Dynamic Values

Laravel allows you to customize the replacement of placeholders in error messages using the Validator::replacer method. To replace :position with the actual index of the array, you need to write a custom validation message replacer.

Here’s how to do that:

Validator::replacer('required', function ($message, $attribute, $rule, $parameters) {
    if (preg_match('/products\.(\d+)\./', $attribute, $matches)) {
        $position = $matches[1] + 1; // Increment index by 1 for human-friendly numbering
        return str_replace(':position', $position, $message);
    }
    return $message;
});

This code snippet captures the index of the product array item and replaces :position in the error message with the correct value.

Step 6: Testing the Validation

To test the validation, you can send a POST request with invalid data for the products array.

POST /store
{
    "products": [
        {"name": "", "price": "abc", "quantity": 0},
        {"name": "Product 2", "price": 15, "quantity": 2}
    ]
}

The validation response will contain dynamic error messages like:

{
    "errors": {
        "products.0.name": ["The product name at position 1 is required."],
        "products.0.price": ["The product price at position 1 is required."],
        "products.0.quantity": ["The product quantity at position 1 must be at least 1."]
    }
}

Step 7: Displaying Validation Errors in the View

To show these error messages in your Blade template, you can use Laravel's standard method for displaying validation errors.

@if ($errors->any())
    <div class="alert alert-danger">
        <ul>
            @foreach ($errors->all() as $error)
                <li>{{ $error }}</li>
            @endforeach
        </ul>
    </div>
@endif

In this article, we explored how to show dynamic error messages in Laravel's array validation by using custom messages and the Validator::replacer method. This method gives you flexibility when working with complex data structures like arrays, making your application more user-friendly by providing clear and contextual error messages.

Following these steps, you can easily implement dynamic error messages in your Laravel application, improving the user experience and making validation errors more understandable.