Ticket #43258: class-wp-output-buffer.php

<?php

class WP_Output_Buffer {

    /**
     * These priorities are suggestions for plugin and theme developers
     * to help modify the output at the right time.
     */
    const DEFAULT_PRIORITIES = array(
        'CONTENT'      => 10,
        'CACHE_BEFORE' => 90000,
        'CACHE'        => 100000,
        'CACHE_AFTER'  => 110000,
    );

    private static $enabled = false;

    public static function enable() {
        self::$enabled = true;
    }

    public function __construct() {
        static $inited;
        if (!$inited) {
            add_action('init', array(
                $this,
                'init'
            ));
            $inited = true;
        }
    }

    public function init() {

        if (self::$enabled) {
            ob_start(array(
                $this,
                "output_callback"
            ));
        }
    }

    public function output_callback($buffer, $phase) {

        if ($phase & PHP_OUTPUT_HANDLER_FINAL || $phase & PHP_OUTPUT_HANDLER_END) {
            return apply_filters('output_buffer', $buffer);
        }

        return $buffer;
    }
}

new WP_Output_Buffer();