System sa tvari ze premenna neexistuje pritom ked existuje

var id;
id = 2;
function newid(cisielko){
   id = cisielko;
}
function mapa(){
   $.get("map.php", function(data){
   document.getElementById('mapa').innerHTML = data;
   });
   setTimeout("mapa()",5000);
}

?><img src='<? echo $gr['block']; ?>.png' title='x:<? echo $ex; ?>y:<? echo $ey; ?>' onClick='if(mod == "p") { this.src = id; $.get("lol.php?x=<? echo $ex; ?>&y=<? echo $ey; ?>&newblock=" + id); } if(mod == "z") { if(this.src != "1.png") { this.src= "1.png"; $.get("lol.php?x=<? echo $ex; ?>&y=<? echo $ey; ?>&newblock=1"); } }'><?

var mod = "p";
.... script ....
mod = "p";
.... else .....
mod = "z";

<br><img src="2.png" onClick='newid(2);'><img src="3.png" onClick='newid(3);'>