public function shift()
    {
        $this->internalDataListUpdate();
        if (isset($this->internalDataListData[0])) {
            $this->internalDataListUpdateValueIfNeeded($this->internalDataListData, 0);
            return array_shift($this->internalDataListData);
        }
        return null;
    }
public function shift()
    {
        $this->internalDataListUpdate();
        if (isset($this->internalDataListData[0])) {
            $this->internalDataListUpdateValueIfNeeded($this->internalDataListData, 0);
            return array_shift($this->internalDataListData);
        }
        return null;
    }
public function shift ( ) { $ this -> internalDataListUpdate ( ) ; if ( isset ( $ this -> internalDataListData [ 0 ] ) ) { $ this -> internalDataListUpdateValueIfNeeded ( $ this -> internalDataListData , 0 ) ; return array_shift ( $ this -> internalDataListData ) ; } return null ; }
Shift an object off the beginning of the list.

@return object|null Returns the shifted object or null if the list is empty.
@throws \InvalidArgumentException
Shift an object off the beginning of the list .