Creating the Singleton design pattern in PHP5

Question

How would one create a Singleton class using PHP5 classes?

Accepted Answer

```
/**
 * Singleton class
 *
 */
final class UserFactory
{
    private static $inst = null;

// Prevent cloning and de-serializing
    private function __clone(){}
    private function __wakeup(){}

/**
     * Call this method to get singleton
     *
     * @return UserFactory
     */
    public static function Instance()
    {
        if ($inst === null) {
            $inst = new UserFactory();
        }
        return $inst;
    }
    
    /**
     * Private ctor so nobody else can instantiate it
     *
     */
    private function __construct()
    {
        
    }
}
```

To use:

```
$fact = UserFactory::Instance();
$fact2 = UserFactory::Instance();
```

`$fact == $fact2;`

But:

```
$fact = new UserFactory()
```

Throws an error.

See http://php.net/manual/en/language.variables.scope.php#language.variables.scope.static to understand static variable scopes and why setting `static $inst = null;` works.

Creating the Singleton design pattern in PHP5

Solution

Problem

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