laravel-slug.php

<?php

namespace App\Services;

use App\Post;

class Slug
{
    /**
     * @param $title
     * @param int $id
     * @return string
     * @throws \Exception
     */
    public function createSlug($title, $id = 0)
    {
        // Normalize the title
        $slug = str_slug($title);

        // Get any that could possibly be related.
        // This cuts the queries down by doing it once.
        $allSlugs = $this->getRelatedSlugs($slug, $id);

        // If we haven't used it before then we are all good.
        if (! $allSlugs->contains('slug', $slug)){
            return $slug;
        }

        // Just append numbers like a savage until we find not used.
        for ($i = 1; $i <= 10; $i++) {
            $newSlug = $slug.'-'.$i;
            if (! $allSlugs->contains('slug', $newSlug)) {
                return $newSlug;
            }
        }

        throw new \Exception('Can not create a unique slug');
    }

    protected function getRelatedSlugs($slug, $id = 0)
    {
        return Post::select('slug')->where('slug', 'like', $slug.'%')
            ->where('id', '<>', $id)
            ->get();
    }
}

I'm write simple trait which you can use in Eloquent models for slug auto-generation.

<?php

namespace App\Models\Traits;

use Illuminate\Database\Eloquent\Model;

/**
 * Trait Sluggable.
 *
 * Sources:
 * @see https://github.com/martinbean/laravel-sluggable-trait/
 * @see https://gist.github.com/ericlbarnes/3b5d3c49482f2a190619699de660ee9f
 * @see https://interworks.com.mk/the-easiest-way-to-create-unique-slugs-for-blog-posts-in-laravel/
 */
trait Sluggable
{
    /**
     * Boot the sluggable trait for a model.
     *
     * @return void
     */
    public static function bootSluggable()
    {
        static::saving(function (Model $model) {
            if (empty($model->getSlug())) {
                $slug = self::generateUniqueSlug($model);

                $model->setSlug($slug);
            }
        });
    }

    /**
     * The name of the column to use for slugs.
     *
     * @return string
     */
    public function getSlugColumnName()
    {
        return 'slug';
    }

    /**
     * Get the string to create a slug from.
     *
     * @return string
     */
    public function getSluggableString()
    {
        return $this->getAttribute('name');
    }

    /**
     * Get the current slug value.
     *
     * @return string
     */
    public function getSlug()
    {
        return $this->getAttribute($this->getSlugColumnName());
    }

    /**
     * Set the slug to the given value.
     *
     * @param  string  $value
     * @return $this
     */
    public function setSlug($value)
    {
        $this->setAttribute($this->getSlugColumnName(), $value);

        return $this;
    }

    /**
     * @param Model $model
     * @return string
     * @throws \Exception
     */
    private static function generateUniqueSlug(Model $model): string
    {
        $slug = empty($model->getSlug()) ? trim(str_slug($model->getSluggableString())) : $model->getSlug();
        $attribute = trim($model->getSlugColumnName());

        if (empty($slug) || empty($attribute)) {
            throw new \Exception('Incorrect slug attribute or sluggable string for model! Check your "fillable" array.');
        }

        $modelsWithRelatedSlug = $model
            ->withoutGlobalScopes()
            ->withTrashed()
            ->where($attribute, 'LIKE', $slug.'%')
            ->get([$attribute]);

        $i = 0;
        while ($modelsWithRelatedSlug->contains($attribute, $slug)) {
            ++$i;
            $matches = [];
            if (preg_match('/^(.*?)-(\d+)$/', $slug, $matches)) {
                $nextNum = $matches[2] + $i;
                $slug = "{$matches[1]}-$nextNum";
            } else {
                $slug = "$slug-$i";
            }
        }

        $model = $model
            ->withoutGlobalScopes()
            ->where($attribute, $slug)
            ->first([$attribute]);

        if ($model) {
            // Still not unique...
            $slug = self::generateUniqueSlug($model);
        }

        return $slug;
    }
}

Usage:

use App\Helpers\CoolSlug;
$slugLibrary = new CoolSlug(\App\Post::class);
return $slugLibrary->createSlug('test');

CoolSlug Class:

<?php
namespace App\Helpers;

class CoolSlug {
    private $entity;

    /**
     * Instantiate a new CoolSlug instance.
     */
    public function __construct($entity) {
        $this->entity = $entity;
    }
    
    /**
     * Generate a URL friendly "slug" from the given string.
     * 
     * @param $title String
     * @return string
     * @throws \Exception
     */
    public function createSlug($title) {
        // Normalize the title
        $slug = \Illuminate\Support\Str::slug($title, '-');

        // Get any that could possibly be related.
        // This cuts the queries down by doing it once.
        $allSlugs = $this->getRelatedSlugs($slug);

        // If we haven't used it before then we are all good.
        if($allSlugs == 0) {
            return $slug;
        }

        // Just append numbers like a savage until we find not used.
        for($i = 1; $i <= 20; $i++) {
            $newSlug = $slug. '-'. $i;
            if($this->getRelatedSlugs($newSlug) == 0) {
                return $newSlug;
            }
        }

        throw new \Exception('Can not create a unique slug.');
    }

    protected function getRelatedSlugs($slug) {
        return call_user_func(array($this->entity, 'select'), 'permalink')->where('permalink', $slug)->count();
    }
}