Unable to save select box options in Laravel 5.1 - php

Question

I am working on my first project using Laravel 5.1. Uses a selectbox in a form.
{!!Form::select('animal_parent[]', array('1' => 'opt1', '2' => 'opt2', '3' => 'opt3', '4' => 'opt4',), null, ['id' => 'animal_parent', 'disabled' => 'disabled', 'multiple' => 'multiple', 'class' => 'form-control'])!!}
Selection limited to two options which need to saved in two columns, male_parent and female_ parent of the animal table.
There are no male_parent and female_ parent element names in the form. Similarly no animal_parent field in animal table.
Values are set as expected in the code given below. However, the insert command does not reflect the newly set values and throws an error.
"ErrorException in helpers.php line 671: preg_replace(): Parameter mismatch, pattern is a string while replacement is an array."
Any help would be much appreciated.
First attempt using mutators
public function setMaleParentAttribute()
{
$parent = Input::get('animal_parent');
$this->attributes['male_parent'] = intval($parent[0]);
}
public function setFemaleParentAttribute(AddAnimalRequest $request)
{
$parent = Input::get('animal_parent);
if (isset($parent[1])) {
$this->attributes['female_parent'] = intval($parent[1]);
} else {
$this->attributes['female_parent'] = intval($parent[0]);
}
unset($request->animal_parent);
}
Second attempt using the store() method in the controller.
$animal = new Animal($request->all());
$parent = Input::get('animal_parent');
$animal['male_parent'] = intval($parent[0]);
if (isset($parent[1])) {
$animal['female_parent'] = intval($parent[1]);
} else {
$animal['female_parent'] = intval($parent[0]);
}
unset($request->animal_parent);
Auth::user()->animals()->save($animal);
return redirect('animals');

Answer 1

The problem was then solved with a change in UI. I feel the problem could have been solved using the below method. Hope that helps someone.
$input = $request->all();
$parent = $input['animal_parent'];
$input['male_parent'] = intval($parent[0]);
if (isset($parent[1])) {
$input['female_parent'] = intval($parent[1]);
} else {
$input['female_parent'] = intval($parent[0]);
}
unset($input['animal_parent']);
$animal = new Animal($input);
$animal->save();`