Craft CMS

**Essential Configuration:**

**1. General Config (config/general.php):**
```php
<?php
use craft\helpers\App;

return [
'*' => [
'defaultWeekStartDay' => 1,
'omitScriptNameInUrls' => true,
'securityKey' => App::env('SECURITY_KEY'),
'cpTrigger' => 'admin',
],
'production' => [
'devMode' => false,
'allowAdminChanges' => false,
'enableTemplateCaching' => true,
],
'dev' => [
'devMode' => true,
'allowAdminChanges' => true,
'enableTemplateCaching' => false,
],
];
```

**2. Database Config (config/db.php):**
```php
<?php
return [
'driver' => App::env('DB_DRIVER'),
'server' => App::env('DB_SERVER'),
'port' => App::env('DB_PORT'),
'database' => App::env('DB_DATABASE'),
'user' => App::env('DB_USER'),
'password' => App::env('DB_PASSWORD'),
'schema' => App::env('DB_SCHEMA'),
'tablePrefix' => App::env('DB_TABLE_PREFIX'),
];
```

**3. Twig Template Example:**
```twig
{# templates/index.twig #}
{% extends "_layout" %}

{% block content %}
<h1>{{ entry.title }}</h1>

{# Matrix field #}
{% for block in entry.contentBlocks.all() %}
{% switch block.type %}
{% case "text" %}
<div class="text-block">
{{ block.text|raw }}
</div>

{% case "image" %}
<figure>
<img src="{{ block.image.one().url }}" alt="{{ block.image.one().title }}">
<figcaption>{{ block.caption }}</figcaption>
</figure>

{% case "gallery" %}
<div class="gallery">
{% for image in block.images.all() %}
<img src="{{ image.url }}" alt="{{ image.title }}">
{% endfor %}
</div>
{% endswitch %}
{% endfor %}
{% endblock %}
```

**4. Querying Entries:**
```twig
{# Get all blog posts #}
{% set posts = craft.entries()
.section('blog')
.orderBy('postDate desc')
.limit(10)
.all() %}

{% for post in posts %}
<article>
<h2>{{ post.title }}</h2>
<p>{{ post.summary }}</p>
<a href="{{ post.url }}">Read more</a>
</article>
{% endfor %}

{# Get related entries #}
{% set relatedPosts = craft.entries()
.section('blog')
.relatedTo(entry)
.limit(3)
.all() %}
```

**5. Asset Transforms:**
```twig
{# Define image transform #}
{% set thumb = {
mode: 'crop',
width: 300,
height: 300,
quality: 80
} %}

<img src="{{ image.url(thumb) }}" alt="{{ image.title }}">

{# Or use named transforms (config/image-transforms.php) #}
<img src="{{ image.url('thumbnail') }}" alt="{{ image.title }}">
```

**6. Multi-Site Configuration:**
```php
<?php
// config/general.php
return [
'*' => [
'siteUrl' => [
'en' => 'https://example.com',
'fr' => 'https://example.com/fr',
'de' => 'https://example.de',
],
],
];
```

**7. Custom Module Example:**
```bash
# Generate module
php craft make module

# config/app.php
return [
'modules' => [
'my-module' => \modules\Module::class,
],
'bootstrap' => ['my-module'],
];
```

**8. Caching:**
```php
<?php
// Enable Redis caching
// config/app.php
use craft\helpers\App;

return [
'components' => [
'cache' => [
'class' => yii\redis\Cache::class,
'redis' => [
'hostname' => 'localhost',
'port' => 6379,
'database' => 0,
],
],
],
];
```

**9. CLI Commands:**
```bash
# Clear caches
php craft clear-caches/all

# Backup database
php craft backup/db

# Restore database
php craft restore/db path/to/backup.sql

# Run migrations
php craft migrate/all

# Generate security key
php craft setup/security-key

# Create admin user
php craft users/create

# Project config sync
php craft project-config/apply
```

**10. Performance Optimization:**
```php
<?php
// config/general.php
return [
'production' => [
'enableTemplateCaching' => true,
'cacheDuration' => 3600,
'maxCachedCloudImageSize' => 2000,
'optimizeImageFilesize' => true,
'transformGifs' => false,
],
];
```

**Best Practices:**
- Use environment variables for sensitive configuration
- Enable `allowAdminChanges => false` in production
- Implement proper image transforms for responsive images
- Use eager loading for related entries to avoid N+1 queries
- Enable template caching in production
- Regular database backups with `php craft backup/db`
- Use Project Config for version controlling settings
- Implement Redis/Memcached for high-traffic sites
- Keep Craft and plugins updated regularly
- Use Matrix fields for flexible content layouts