The colon-based syntax was voted down. What went live in 5.4 was support for brackets in lieu of array() // Typical array syntax $arr = array('key' =>

The colon-based syntax was voted down. What went live in 5.4 was support for brackets in lieu of array() // Typical array syntax $arr = array('key' => 'asdf'); // Supported in 5.4+ $arr = ['key' => 'asdf'];