Not sure if this helps but...
You can make it so when it reaches a certain level, the level is called something so it would kind of be like if the pet evolved, it would sort of be like the species name changed... (although the type of pet wouldn't change, just each level would be given a name).
So you could say...
PHP Code:
if($currentlevel == "0"){
$levelname="Level 1";
}
else if($currentlevel == "1"){
$levelname="Level 2";
}
And then use $levelname whenever you refer to the level.