Fix zero-extension on range() char parameters

Author: ndossche

ext/standard/array.c

@@ -3049,9 +3049,9 @@ PHP_FUNCTION(range)
 			goto handle_numeric_inputs;
 		}
 
-		/* Generate array of characters, as ints to make bounds checking possible in the loop condition */
-		int low = Z_STRVAL_P(user_start)[0];
-		int high = Z_STRVAL_P(user_end)[0];
+		/* Generate array of characters, as zero-extended ints to make bounds checking possible in the loop condition */
+		int low = (unsigned char) Z_STRVAL_P(user_start)[0];
+		int high = (unsigned char) Z_STRVAL_P(user_end)[0];
 
 		/* Decreasing char range */
 		if (low > high) {