Both ways are same.
And both ways should work.
$ailment["Poison"]=0;
$ailment["Syphon"]=0;
$ailment["Fatigue"]=0;
No problem. Correct php syntax! Should work.
This is exactly the same as above, but should be like this
$ailment=array("Poison"=>0, "Syphon"=>0, "Fatigue"=>0);