file_get_contents(http://localhost:51089): no such host is known - php

Question

I am following step-by-step guide of google app engine "Using the User Service", but after I ran the app server locally
C:\Users\xxx>dev_appserver.py --php_exectuable_path="C:\Users\xxx\Desktop\php54\php-cgi.exe" C:\Users\xxx\Desktop\FirstPhpPrj\
below errors pop up:
Warning: file_get_contents(): php_network_getaddresses: getaddrinfo failed:
No such host is known. in <b>C:\Users\xxx\Desktop\google_appengine\php\sdk\
google\appengine\runtime\RemoteApiProxy.php</b> on line 92
Warning:
file_get_contents(http://localhost:51089)
: failed to open stream:
php_network_getaddresses: getaddrinfo failed: No such host is known. in C
:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\runtime\RemoteApiP
roxy.php on line 92
Fatal error: Uncaught exception 'google\net\ProtocolBufferDecodeError'
with message 'Not initialized: login_url' in C:\Users\xxx\Desktop\google_appengin
e\php\sdk\google\appengine\runtime\proto\ProtocolMessage.php:121
Stack trace:
#0 C:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\runtime\proto\
ProtocolMessage.php(88): google\net\ProtocolMessage->mergeFromString('')
#1 C:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\runtime\Remote
ApiProxy.php(109): google\net\ProtocolMessage->parseFromString('')
#2 C:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\runtime\ApiProxy.php(42): google\appengine\runtime\RemoteApiProxy->makeSyncCall('user', 'CreateLoginURL', Object(google\appengine\CreateLoginURLRequest), Object(google\app
engine\CreateLoginURLResponse), NULL)
#3 C:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\api
\users\UserService.php(69): google\appengine\runtime\ApiProxy::makeSyncCall('user', 'CreateLoginURL', Object(google\appengine\CreateLoginURLRequest), Object(google in C
:\Users\xxx\Desktop\google_appengine\php\sdk\google\appengine\runtime\proto\ProtocolMessage.php on line 121
I browsed the log, there are two warnings and one fatal error. But not after I looked thru the coding of php sdk, i realized that this fatal error, caused by empty string input in "mergeFromString", is in fact caused by the warnings of"
file_get_contents(http://localhost:51089)
no such host is known", because in RemoteApiProxy.php, function CreateLoginURLResponse:
$serialized_remote_respone = file_get_contents(
'http://localhost:' . $this->apiPort, false, $context);
once serialized_remote_response gets an empty result, it will affect the command in next line:
$remote_response->parseFromString($serialized_remote_respone);
In this case, my own codes are actually irrelevant as it is exactly the same as the google sample codes:here.
I just want to figure out why on earth, after google app engine starts its API server at
http://localhost:51089
yet it is not recognized! I tried pin this host and windows also threw error!