Converts a PHP variable into its JavaScript equivalent.
We use HTML-safe strings, with several characters escaped.
function drupal_json_encode($var) {
// Encode <, >, ', &, and " using the json_encode() options parameter.
return json_encode($var, JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP | JSON_HEX_QUOT);
}