Defining Relationships: One To Many (Inverse)

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Comment extends Model
{
    /**
     * Get the post that owns the comment.
     */
    public function post()
    {
        return $this->belongsTo('App\Post');
    }
}

/**
 * Get the post that owns the comment.
 */
public function post()
{
    return $this->belongsTo('App\Post', 'foreign_key');
}

/**
 * Get the post that owns the comment.
 */
public function post()
{
    return $this->belongsTo('App\Post', 'foreign_key', 'other_key');
}

$comment = App\Comment::find(1);

echo $comment->post->title;