phpjs/experimental/outcontrol/ob_get_contents.js

php.js offers community built php functions in javascript

function ob_get_contents() {
  // http://kevin.vanzonneveld.net
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // *     example 1: ob_get_contents();
  // *     returns 1: 'some buffer contents'

  this.php_js = this.php_js || {};
  var phpjs = this.php_js,
      ini = phpjs.ini,
      obs = phpjs.obs;
  if (!obs || !obs.length) {
    return (ini && ini.output_buffering && (typeof ini.output_buffering.local_value !== 'string' || ini.output_buffering.local_value.toLowerCase() !== 'off')) ? '' : false; // If output was already buffered, it would be available in obs
  }
  return obs[obs.length - 1].buffer; // Retrieve most recently added buffer contents
}