PHPpaypalipn returns INVALID, but payment_status = Completed. why?

This is the recorded log: [082220129: 53PM] Here is the recorded log:
[08/22/2012 PM]-FAIL: IPN Validation Failed.
Ipn post Vars from Paypal:

mc_gross=1.00, protection_eligibility=Eligible, address_status=confirmed, payer_id=N9MJ3E2F72RSA, tax=0.00, address_street=1 Main St, payment_date=21:53:35 Aug 22, 2012 PDT, **payment_status=Completed**, charset=windows-1252, address_zip=95131, first_name=buyer, mc_fee=0.33, address_country_code=US, address_name=buyer buyer, notify_version=3.6, custom=3ba049446d1a922fccf9233c32794f16, payer_status=verified, business=775357_1345694569_biz@qq.com, address_country=United States, address_city=San Jose, quantity=1, verify_sign=ALJkApMs7H6RB6yOv.fdCxcGTa-tANEn6Te6SHeQgyIYAwZVU3TIrY0A, payer_email=775357_1345694424_per@qq.com, txn_id=60Y885950A771745Y, payment_type=instant, last_name=buyer, address_state=CA, receiver_email=775357_1345694569_biz@qq.com, payment_fee=0.33, receiver_id=BPFVTFG92JFY4, txn_type=web_accept, item_name=xxx, mc_currency=USD, item_number=, residence_country=US, test_ipn=1, handling_amount=0.00, transaction_subject=3ba049446d1a922fccf9233c32794f16, payment_gross=1.00, shipping=0.00, ipn_track_id=f9305268979, **IPN Response from Paypal Server:** HTTP/1.1 200 OKDate: Thu, 23 Aug 2012 04:53:40 GMTServer: ApacheX-Frame-Options: SAMEORIGINSet-Cookie: c9MWDuvPtT9GIMyPc3jwol1VSlO=H9KuMTssqUu_tJf3Dam9rchmDS6GUQFouM5-KC3TtpHU199YtckVmNrqgSLfY9uIOFULbrXej6jtUILOdz4ImR-ruvjgSDh7RWeuAzPIVo40F7nN8Jxn1xVY2n-Ak8kFLmkUEm%7cSrCbIFQ6eG7qVUKiU5gXgRuZnXVRhIVr3AsqzO7z4At6yvgs588DjotxRox8tl_hJ4qi30%7cptKiyBJFIzge516dKd0-8zfnmTwVxF8Viz_QKeMZPIZPZ5Iu9OcdYiQyE8g861Be04KEt0%7c1345697620; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: cookie_check=yes; expires=Sun, 21-Aug-2022 04:53:40 GMT; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: navcmd=_notify-validate; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: navlns=0.0; expires=Wed, 18-Aug-2032 04:53:40 GMT; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: Apache=10.72.109.11.1345697620182214; path=/; expires=Sat, 16-Aug-42 04:53:40 GMTConnection: closeTransfer-Encoding: chunkedContent-Type: text/html; charset=UTF-87**INVALID**0

Reply content:

Here is the recorded log:
[08/22/2012 PM]-FAIL: IPN Validation Failed.
Ipn post Vars from Paypal:

mc_gross=1.00, protection_eligibility=Eligible, address_status=confirmed, payer_id=N9MJ3E2F72RSA, tax=0.00, address_street=1 Main St, payment_date=21:53:35 Aug 22, 2012 PDT, **payment_status=Completed**, charset=windows-1252, address_zip=95131, first_name=buyer, mc_fee=0.33, address_country_code=US, address_name=buyer buyer, notify_version=3.6, custom=3ba049446d1a922fccf9233c32794f16, payer_status=verified, business=775357_1345694569_biz@qq.com, address_country=United States, address_city=San Jose, quantity=1, verify_sign=ALJkApMs7H6RB6yOv.fdCxcGTa-tANEn6Te6SHeQgyIYAwZVU3TIrY0A, payer_email=775357_1345694424_per@qq.com, txn_id=60Y885950A771745Y, payment_type=instant, last_name=buyer, address_state=CA, receiver_email=775357_1345694569_biz@qq.com, payment_fee=0.33, receiver_id=BPFVTFG92JFY4, txn_type=web_accept, item_name=xxx, mc_currency=USD, item_number=, residence_country=US, test_ipn=1, handling_amount=0.00, transaction_subject=3ba049446d1a922fccf9233c32794f16, payment_gross=1.00, shipping=0.00, ipn_track_id=f9305268979, **IPN Response from Paypal Server:** HTTP/1.1 200 OKDate: Thu, 23 Aug 2012 04:53:40 GMTServer: ApacheX-Frame-Options: SAMEORIGINSet-Cookie: c9MWDuvPtT9GIMyPc3jwol1VSlO=H9KuMTssqUu_tJf3Dam9rchmDS6GUQFouM5-KC3TtpHU199YtckVmNrqgSLfY9uIOFULbrXej6jtUILOdz4ImR-ruvjgSDh7RWeuAzPIVo40F7nN8Jxn1xVY2n-Ak8kFLmkUEm%7cSrCbIFQ6eG7qVUKiU5gXgRuZnXVRhIVr3AsqzO7z4At6yvgs588DjotxRox8tl_hJ4qi30%7cptKiyBJFIzge516dKd0-8zfnmTwVxF8Viz_QKeMZPIZPZ5Iu9OcdYiQyE8g861Be04KEt0%7c1345697620; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: cookie_check=yes; expires=Sun, 21-Aug-2022 04:53:40 GMT; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: navcmd=_notify-validate; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: navlns=0.0; expires=Wed, 18-Aug-2032 04:53:40 GMT; domain=.paypal.com; path=/; Secure; HttpOnlySet-Cookie: Apache=10.72.109.11.1345697620182214; path=/; expires=Sat, 16-Aug-42 04:53:40 GMTConnection: closeTransfer-Encoding: chunkedContent-Type: text/html; charset=UTF-87**INVALID**0

In fact, IPN is recommended because it is asynchronous, and can avoid transaction status update failures caused by network problems.

You receive the invalid Response. The official check method is as follows:

1. Check that your are posting your response to the correct URL, which is https://www.sandbox.paypal.com/cgi-bi... or https://www.paypal.com/cgi-bin/webscr... depending on whether you are testing in the Sandbox or you are live, respectively.
2. Verify that your response contains exactly the same IPN variables and values in the same order, preceded with cmd = _ policy-validate.
3. Ensure that you are encoding your response string and are using the same character encoding as the original message.

Suddenly you see test_ipn = 1 in your response, which means you used it to test paypal, but your response was actually received from paypal.com, of course, Invalid. Change your receiving address to sandbox.paypal.com.

IPN is not safe. we recommend that you use PDT ~

Hello, how did you obtain this IPN? I have never been able to get it .. Could you tell me? Very urgent. thank you !!