Getting Bash error while running PHP application

I just began using c9 tried running following php code with runner PHP-CLI getting bash error

(standard_in) 1: syntax error
bash: line 9: [: -eq: unary operator expected

Kindly guide how to fix

<?php

print(‘Hello, World!’);

print("\nThe sum of 2 and 3 is 5.");

$sum = (int)$argv[1] + (int)$argv[2];

print("\nThe sum of $argv[1] and $argv[2] is $sum.");
?>