move demo documents into separate files

demo/docs/php.php

@@ -0,0 +1,19 @@
+<?php
+
+function nfact($n) {
+    if ($n == 0) {
+        return 1;
+    }
+    else {
+        return $n * nfact($n - 1);
+    }
+}
+
+echo "\n\nPlease enter a whole number ... ";
+$num = trim(fgets(STDIN));
+
+// ===== PROCESS - Determing the factorial of the input number =====
+$output = "\n\nFactorial " . $num . " = " . nfact($num) . "\n\n";
+echo $output;
+
+?>