Attach an SplObserver

# SplSubject::attach

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

SplSubject::attach — Attach an SplObserver

### Description

public SplSubject::attach(SplObserver `$observer`): void

Attaches an SplObserver so that it can be notified of updates.

Warning

This function is currently not documented; only its argument list is available.

### Parameters

`observer`

  The SplObserver to attach.

### Return Values

No value is returned.

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