Example of dynamically generated function in php

$a['a']=1;
$a['b']=1;
$a['c']=1;
$str="function a(){global $a;if($a['a']==1 && $a['b']==1 && $a['c']==1){return 'OK';}else{return 'ERR';}}";
eval($str);
if(a()=="OK"){
 echo "GOOD";
}else{
 echo "OH NO";
}