$suburbInsert = array();
$suburbInsert[] = array(

    'name' => $postalCode . ' ' . $suburbName,
    'suburb_name' => $suburbName,
    'pcode' => $postalCode

);

$suburbID = DB::table('suburbs')->insertGetId( $suburbInsert );

{"error":{"type":"ErrorException","message":"preg_replace(): Parameter mismatch, pattern is a string while replacement is an array","file":"/var/www/laravel/vendor/laravel/framework/src/Illuminate/Support/helpers.php","line":990}}