Thanks! I got it. For example, we need to share the property  `protected static $messageIndex = 1;` between handlers. Also the property `$initialized` has to be shared.

But cannot the static property `$sendHeaders` be easily replaced with the call to `$this->headersAccepted()`?

Another solution would be to initialize the `$sendHeaders` property each time we write a record: (*FirePhpHandler:135-136*)
```
    protected function write(array $record)
    {
        $this->sendHeaders = $this->headersAccepted();
        // WildFire-specific headers must be sent prior to any messages
        if (!self::$initialized) {
      
```
instead of 
```
    protected function write(array $record)
    {
        // WildFire-specific headers must be sent prior to any messages
        if (!self::$initialized) {
            self::$sendHeaders = $this->headersAccepted();
            ...
```
Don't get me wrong, I just try to avoid methods where possible. :)