phpjs/workbench/session/session_name.js

php.js offers community built php functions in javascript

function session_name(name) {
  // +   original by: Brett Zamir (http://brett-zamir.me)
  // *     example 1: session_name('aNewSess');
  // *     returns 1: 'PHPSESSID'

  if (name && ((/^\d+$/).test(name) || !(/^[a-zA-Z0-9]+$/).test(name))) { // if underscore ok, use \W; if need one letter, must it be at beginning?
    throw 'Session name must consist of alphanumeric characters only (and at least one letter)';
  }
  var oldSessionName = '';

  // BEGIN REDUNDANT
  if (!this.php_js) {
    this.php_js = {};
  }
  if (!this.php_js.ini) {
    this.php_js.ini = {};
  }
  if (!this.php_js.ini['session.name']) {
    this.php_js.ini['session.name'] = {};
  }
  // END REDUNDANT

  if (this.php_js.ini['session.name'].local_value) {
    oldSessionName = this.php_js.ini['session.name'].local_value;
  }

  if (name) {
    this.php_js.ini['session.name'].local_value = name;
  }
  return oldSessionName || 'PHPSESSID';
}