Allow to modify HTML in output buffer

Hey @mguenter

First we would like to point that we are very happy when other plugin developers are working on making their products compatible with ours. Thank you for the efforts you have put on this so far.

However, what you’re suggesting is not the best way to achieve what you’re after. We’re applying all our optimizations via this parser and adding the option to modify it will endanger the overall functionality of the plugin. That’s why I am afraid we won’t be able to provide the requested filter.

We are using default priority of 10 to open and close/flush the buffer, so you can open a new one with priority of 11 and modify the HTML content after it is being returned from our plugin.

This way some incompatibilities can be avoided and each plugin will handle its own changes only.

Do not rely on the shutdown action to close the buffer. Instead of modifing the output and wait for WordPress to close it, use one of the recommended buffering functions.

The contents of this internal buffer may be copied into a string variable using ob_get_contents(). To output what is stored in the internal buffer, use ob_end_flush(). Alternatively, ob_end_clean() will silently discard the buffer contents.

The reason why shutdown action closes the buffering is to prevent forgotten opened buffers, Do not rely on it, it’s there to prevent a white screen…

add_action(
    'init',
    [$this->getBlocker(), 'registerOutputBuffer'],
    11
);

add_action(
    'shutdown',
    [$this->getBlocker(), 'closeOutputBuffer'],
    11
);

public function registerOutputBuffer() {
    if ($this->isEnabled()) {
        \ob_start([$this, 'ob_start']);
    }
}

public function ob_start($response) {
    // do whatever the plugin does

    return $modified_html;
}

public function closeOutputBuffer() {
    if ( ob_get_length() ) {
        ob_end_flush();
    }
}