That is just a warning and it can probably be ignored if everything works. However I can still probably fix it. Try changing that line from:
if (strpos($SessionVal,"<".strtolower($paramName))>=0 && strpos($SessionVal,"</"+strtolower($paramName))>=0) {
to:
if (strpos($SessionVal,"<".strtolower($paramName)) !== false && strpos($SessionVal,"</"+strtolower($paramName)) !== false) {