Datovalidering igen igen

Jeg har set et eksempel som erik har lavet i ASP på datovalidering:

<%

  function two(s)
    if len(s)=1 then
      two="0" & s
    else
      two=s
    end if
  end function

  function datotjek(dato)
    dim regex,matches,match
    set regex = new regexp
    regex.pattern = "^ *([0-9]{4})-([0-9]{1,2})-([0-9]{1,2}) *$"
    regex.global = false
    regex.ignorecase = false

    set matches = regex.execute(dato)

    if matches.count>0 then
      set match=matches(0)
      datotjek=match.submatches(0) & "-" & two(match.submatches(1)) & "-" & two(match.submatches(2))
      set matches=nothing
      exit function
    end if
    set matches=nothing

    regex.pattern = "^ *([0-9]{4})([0-9]{2})([0-9]{2}) *$"

    set matches = regex.execute(dato)

    if matches.count>0 then
      set match=matches(0)
      datotjek=match.submatches(0) & "-" & two(match.submatches(1)) & "-" & two(match.submatches(2))
      set matches=nothing
      exit function
    end if
    set matches=nothing

   
regex.pattern = "^ *([0-9]{1,2})-([0-9]{1,2})-([0-9]{4}) *$"

    set matches = regex.execute(dato)

    if matches.count>0 then
      set match=matches(0)
      datotjek=match.submatches(2) & "-" & two(match.submatches(1)) & "-" & two(match.submatches(0))
      set matches=nothing
      exit function
    end if
    set matches=nothing

    datotjek="FEJL"
  end function
 
  response.write datotjek("2004-06-01") & "<br>"
  response.write datotjek("  2004-6-1  ") & "<br>"
  response.write datotjek("  20040601  ") & "<br>"
  response.write datotjek("  1-6-2004  ") & "<br>"
  response.write datotjek("  øllebrød  ") & "<br>"

%>

- er der nogen der vil hjælpe mig med at omskrive det til PHP?