I think Grief means something like the following:

PHP Code:
//MADE BY IMASK
//REVISED BY NOOF*
//#CLIENTSIDE    //TIP ALWAYS CHECK THIS TO MAKE SURE IT IS SPELLED CORRECTLY!!

function onCreated() {
  this.image = "door.png";
  this.open = false; //make sure this starts false when the script runs
}

function onPlayerChats() {
  if (player.chat == "/open" && clientr.staff == 1) {
    this.open = true;
    onCheck();
  } else if (player.chat == "/close" && clientr.staff == 1) {
    this.open = false;
    onCheck();
  }
}

function onCheck() {
  if (this.open == true) {
    this.image.show();
  } else if (this.open == false) {
    this.image.hide();
  }
} 
Check out the booleans (the = true and = false), and practice them they are important in the future.

Also as Grief mentioned the
PHP Code:
if(..) {

} else if(...) {

} 
Is always your friend, reason being it looks cleaner and what can go wrong using less amount of code?

Hope this helps and Good luck your doing great!