using strpos instead of substr_count

don't know if it's faster, but I don't see a reason to count the number of times a line exists in a file for our use case.

scan.php

@@ -173,8 +173,7 @@ class MalwareScanner
             if ($toSearch[0] === '#') {
                 continue;
             }
-            $substrCount = substr_count($fileContent, $toSearch);
-            if ($substrCount > 0) {
+            if (strpos($fileContent, $toSearch) !== FALSE){
                 $found = true;
                 break;
             }