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Yii3 - How to start

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Yii3 - How to start

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[...]
First of all, learn what [PHP Standards Recommendations](https://en.wikipedia.org/wiki/PHP_Standard_Recommendation) by [Framework Interoperability Group (FIG)](https://www.php-fig.org/psr) are. It will help you understand why so many "weird" PSR imports are in the Yii3 code. In short: These interfaces help authors of different frameworks to write compatible classes so they can be reused in any other framework following these principles.

## Dependency injection + container
Check [this YouTube video](https://www.youtube.com/watch?v=TqMXzEK0nsA) for explanation

## Cconstruct vs I() and invoke() It may be confusing that some classes contain both methods. Note that "property promotion" should be only used in `__construct()`.
 
Magic method `__invoke()` is only used if you create an instance and then use it as a function. Example if the reader does not have experiences with invoking. Just like me a few days ago. The `__invoke()` is called when you call the **instance** as a method. Like this: ```php $obj = new MyObj(); // Now the __construct() is executed. $obj(); // Now the __invoke() is executed
 
```
 
 
To be honest, I still do not fully understand the real purpose of this situa (The instance is needed!)
 
```
 
 
I never used it, but prepared a following example that shows when invoking can be applied:
 
 
```php
 
class MyUpper
 
{
 
    public function __invoke($a) { return $this->go($a); }
 
    public function go($a) { return strtoupper($a); }
 
}
 
$instance = new MyUpper();
 
$array = ['a', 'B', 1, '1'];
 
 
var_dump($instance($array[0]));
 
var_dump(array_map($instance, $array)); // __invoke is used
 
 
// These do the same:
 
var_dump(array_map('strtoupper', $array));
 
var_dump(array_map([$instance, 'go'], $array));
 
var_dump(array_map(function($a) use ($instance) { return $instance->go($a); }, ['a','B',1,'1']));
 
```
 
 
Note that "property promotion" should be only used in `__construct()` just like the dependency injection.
 
## Hash annotations for class attributes
PHP 8 introduces annotations like this (not only for class attributes):

- `#[Column(type: 'primary')]`
- `#[Column(type: 'string(255)', nullable: true)]`
- `#[Entity(repository: UserRepository::class)]`
[...]
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Version: 3.0
Category: Tutorials
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Written by: rackycz rackycz
Last updated by: rackycz rackycz
Created on: Oct 8, 2025
Last updated: 2 months ago
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