src/Northern/Common/Util/ArrayUtil.php
public static function keys($array, $prefix = null)
    {
        $keys = array_keys($array);

        if (! empty($prefix)) {
            $keys = static::prefix($keys, $prefix);
        }

        return $keys;
    }
public static function keys($array, $prefix = null)
    {
        $keys = array_keys($array);

        if (! empty($prefix)) {
            $keys = static::prefix($keys, $prefix);
        }

        return $keys;
    }
public static function keys ( $ array , $ prefix = null ) { $ keys = array_keys ( $ array ) ; if ( ! empty ( $ prefix ) ) { $ keys = static :: prefix ( $ keys , $ prefix ) ; } return $ keys ; }
This method will return all the keys of a given array and optionally
prefix each key with a specified prefix.

@param  array  $array
@param  string $prefix
@return array
This method will return all the keys of a given array and optionally prefix each key with a specified prefix .