add gettype PHP

PHP/README.md

@@ -1,3 +1,4 @@
 # PHP
 
-## ...
+## std
+- [`gettype`](gettype.php) - Get the type of a variable

PHP/gettype.php

@@ -0,0 +1,18 @@
+<?php
+  // gettype(mixed $value): string
+  $value = 1;
+
+  // Return Values
+  // Possible values for the returned string are:
+  //
+  // "boolean"
+  // "integer"
+  // "double" (for historical reasons "double" is returned in case of a float, and not simply "float")
+  // "string"
+  // "array"
+  // "object"
+  // "resource"
+  // "resource (closed)" as of PHP 7.2.0
+  // "NULL"
+  // "unknown type"
+?>