Sets the JSONP callback.
string $callback:
public function setCallback($callback = null) {
if (null !== $callback) {
// taken from http://www.geekality.net/2011/08/03/valid-javascript-identifier/
$pattern = '/^[$_\\p{L}][$_\\p{L}\\p{Mn}\\p{Mc}\\p{Nd}\\p{Pc}\\x{200C}\\x{200D}]*+$/u';
$parts = explode('.', $callback);
foreach ($parts as $part) {
if (!preg_match($pattern, $part)) {
throw new \InvalidArgumentException('The callback name is not valid.');
}
}
}
$this->callback = $callback;
return $this
->update();
}