Add syntax declaration to code block in README.md

README.md

@@ -19,17 +19,19 @@ Features
 Example
 -------
 
-    // Modbus master UDP
-    $modbus = new ModbusMaster("192.168.1.1", "UDP"); 
-    // Read multiple registers
-    try {
-        $recData = $modbus->readMultipleRegisters(0, 12288, 5); 
-    }
-    catch (Exception $e) {
-        // Print error information if any
-        echo $modbus;
-        echo $e;
-        exit;
-    }
-    // Print data in string format
-    echo PhpType::bytes2string($recData);
+```php
+ // Modbus master UDP
+ $modbus = new ModbusMaster("192.168.1.1", "UDP"); 
+ // Read multiple registers
+ try {
+     $recData = $modbus->readMultipleRegisters(0, 12288, 5); 
+ }
+ catch (Exception $e) {
+     // Print error information if any
+     echo $modbus;
+     echo $e;
+     exit;
+ }
+ // Print data in string format
+ echo PhpType::bytes2string($recData);
+```