Efficiently Aggregate Related Data with `withCount`, `withSum`, and `withMax`

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    protected $fillable = ['title'];

    public function comments()
    {
        return $this->hasMany(Comment::class);
    }
}

class Comment extends Model
{
    protected $fillable = ['post_id', 'content', 'likes'];

    public function post()
    {
        return $this->belongsTo(Post::class);
    }
}

// Setup some dummy data
$post1 = Post::create(['title' => 'My First Post']);
$post1->comments()->create(['content' => 'Great post!', 'likes' => 10]);
$post1->comments()->create(['content' => 'Loved it.', 'likes' => 5]);

$post2 = Post::create(['title' => 'Another Post']);
$post2->comments()->create(['content' => 'Interesting read.', 'likes' => 20]);

// Get posts with their comments count
$postsWithCounts = Post::withCount('comments')->get();
foreach ($postsWithCounts as $post) {
    echo "Post: {$post->title}, Comments Count: {$post->comments_count}
";
}

echo "
";

// Get posts with total likes on comments, aliasing the result column
$postsWithLikesSum = Post::withSum('comments as total_comment_likes', 'likes')->get();
foreach ($postsWithLikesSum as $post) {
    echo "Post: {$post->title}, Total Comment Likes: {$post->total_comment_likes}
";
}

echo "
";

// Get posts with the latest comment creation date
$postsWithLatestComment = Post::withMax('comments as latest_comment_at', 'created_at')->get();
foreach ($postsWithLatestComment as $post) {
    echo "Post: {$post->title}, Latest Comment At: {$post->latest_comment_at}
";
}

echo "
";

// Multiple aggregations in a single query
$postsWithAggregates = Post::withCount('comments')
                           ->withSum('comments as total_likes', 'likes')
                           ->withAvg('comments as average_likes', 'likes')
                           ->get();
foreach ($postsWithAggregates as $post) {
    echo "Post: {$post->title}, Comments: {$post->comments_count}, Total Likes: {$post->total_likes}, Avg Likes: {$post->average_likes}
";
}