Insert a new record if not exist and don't update if exist, laravel eloquent

Use the firstOrCreate method for that:

$user = User::firstOrCreate(['name' => 'John Doe']);

If you want to know whether the user was created or fetched, check the wasRecentlyCreated property:

if ($user->wasRecentlyCreated) {
    // "firstOrCreate" didn't find the user in the DB, so it created it.
} else {
    // "firstOrCreate" found the user in the DB and fetched it.
}

In Laravel 5.2 you have the updateOrCreate method from Builder.php, it uses the firstOrNew method to verify if the given attributes exists in db and update the records with the given values or create and save the new records.

The weird thing is that updateOrCreate doesn't appear in the docs:

https://laravel.com/docs/5.2/eloquent#inserting-and-updating-models

/**
 * Create or update a record matching the attributes, and fill it with values.
 *
 * @param  array  $attributes
 * @param  array  $values
 * @return \Illuminate\Database\Eloquent\Model
 */
public function updateOrCreate(array $attributes, array $values = [])
{
    $instance = $this->firstOrNew($attributes);

    $instance->fill($values)->save();

    return $instance;
}