Solving the Issue of Potentially Polymorphic Calls in Laravel PHP

Potentially polymorphic calls can cause runtime issues when the expected class instance lacks the required properties or methods. Proper PHPDoc annotations and type hinting solve this problem efficiently.

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The Problem

Consider the following method:

/**
 * Add credits to the user account.
 *
 * @param  TransactionDetail  $transactionDetail
 * @return void
 */
protected function addCredits(TransactionDetail $transactionDetail): void
{
    $user = $transactionDetail->transaction
        ->user()
        ->lockForUpdate()
        ->firstOrFail();

    $creditsToAdd = $transactionDetail->item->credit_value * $transactionDetail->quantity;
    /**
    The problemlies on the below line 
    */    
    $user->credit_balance += $creditsToAdd; 
    $user->save();
}

If $transactionDetail->transaction or $transactionDetail->item returns an unexpected type, runtime errors occur.

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Solution: Adding PHPDoc Annotations

To ensure type safety, explicitly document properties in the models:

Example Fix

/**
 * Add credits to the user account.
 *
 * @param  TransactionDetail  $transactionDetail
 * @return void
 */
protected function addCredits(TransactionDetail $transactionDetail): void
{
    /** @var User $user */
    $user = $transactionDetail->transaction
        ->user()
        ->lockForUpdate()
        ->firstOrFail();

    $creditsToAdd = $transactionDetail->item->credit_value * $transactionDetail->quantity;
    $user->credit_balance += $creditsToAdd;
    $user->save();
}

By adding /** @var User $user */, we clarify the expected type, ensuring IDE support and runtime safety.

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Conclusion

Proper PHPDoc annotations eliminate these kind of issues, improve IDE autocompletion, and minimize runtime errors.