How to Check for the Existence of a Related Model in Laravel?

Laravel: Checking for the Existence of a Related Model

When building Laravel models with relationships, determining the existence of a related model is crucial for handling updates and creations. In scenarios where the related model might not initially exist, it becomes necessary to check its presence.

Solution for PHP 7.2 and Above:

For PHP 7.2 onwards, a straightforward solution is to utilize the exists() method on the relation object:

<code class="php">$model->relation()->exists();</code>

Generic Solution for Pre-PHP 7.2:

For versions prior to PHP 7.2, a generic solution applicable to all relation types exists:

<code class="php">if (count($model->relation))
{
  // exists
}</code>

Understanding the Evaluations:

• Single Relations: If the related model exists, count() returns 1 (true). If it doesn't exist, count() returns 0 (false).
• To-Many Relations: When there are no related models, count() returns 0 (false), indicating a non-existent collection. If there are related models, count() returns a positive integer (true), regardless of the number of models.

Sample Usage:

In your scenario, you can use the following code to check for the existence of an option model:

<code class="php">if (Input::has('option')) {
    if ($model->option()->exists()) {
        // update option
    } else {
       // create option
    }
};</code>

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