我在沙盒模式下使用paypal pro。我为api设置了正确的api用户名，密码和签名。
我使用的是演示信用卡号：＆＃39; 4111111111111111＆＃39;，cvv no：＆＃39; 123＆＃39;，ex date：01/2016。但有时候回复是空白的。我正在使用AngellEYE_PHPClass。响应数组如下。
阵 （ [错误] =＆gt;排列 （ ）
[REQUESTDATA] => Array
(
[USER] => ######################
[PWD] => #################
[VERSION] => ###############
[BUTTONSOURCE] => AngellEYE_PHPClass
[SIGNATURE] => #######################
[METHOD] => CreateRecurringPaymentsProfile
[TOKEN] =>
[SUBSCRIBERNAME] => Tom Company XX
[PROFILESTARTDATE] => 2014-11-25 23:29:21
[PROFILEREFERENCE] =>
[DESC] => Subscription For business
[MAXFAILEDPAYMENTS] => 2
[AUTOBILLAMT] =>
[TRIALBILLINGPERIOD] =>
[TRIALBILLINGFREQUENCY] =>
[TRIALTOTALBILLINGCYCLES] =>
[TRIALAMT] =>
[BILLINGPERIOD] => Month
[BILLINGFREQUENCY] => 1
[TOTALBILLINGCYCLES] => 0
[AMT] => 5.00
[CURRENCYCODE] => USD
[SHIPPINGAMT] =>
[TAXAMT] =>
[INITAMT] =>
[FAILEDINITAMTACTION] =>
[CREDITCARDTYPE] => Visa
[ACCT] => ########################
[EXPDATE] => 012016
[CVV2] => 123
[STARTDATE] =>
[ISSUENUMBER] =>
[EMAIL] => #####################
[PAYERID] =>
[PAYERSTATUS] =>
[BUSINESS] =>
[SALUTATION] =>
[FIRSTNAME] => Tom Company
[MIDDLENAME] =>
[LASTNAME] => Tom Company
[SUFFIX] =>
[STREET] => Kolkata
[STREET2] =>
[CITY] => Kolkata
[STATE] => West Bengal
[COUNTRYCODE] => IN
[ZIP] => 700001
[PHONENUM] =>
[SHIPTONAME] =>
[SHIPTOSTREET] =>
[SHIPTOSTREET2] =>
[SHIPTOCITY] =>
[SHIPTOSTATE] =>
[SHIPTOZIP] =>
[SHIPTOCOUNTRY] =>
[SHIPTOPHONENUM] =>
)
[RAWREQUEST] => USER=#############&PWD=############&VERSION=##########&BUTTONSOURCE=AngellEYE_PHPClass&SIGNATURE=#####################################&METHOD=CreateRecurringPaymentsProfile&TOKEN=&SUBSCRIBERNAME=Tom+Company+XX&PROFILESTARTDATE=2014-11-25+23%3A29%3A21&PROFILEREFERENCE=&DESC=Subscription+For+business&MAXFAILEDPAYMENTS=2&AUTOBILLAMT=&TRIALBILLINGPERIOD=&TRIALBILLINGFREQUENCY=&TRIALTOTALBILLINGCYCLES=&TRIALAMT=&BILLINGPERIOD=Month&BILLINGFREQUENCY=1&TOTALBILLINGCYCLES=0&AMT=5.00&CURRENCYCODE=USD&SHIPPINGAMT=&TAXAMT=&INITAMT=&FAILEDINITAMTACTION=&CREDITCARDTYPE=Visa&ACCT=4111111111111111&EXPDATE=012016&CVV2=123&STARTDATE=&ISSUENUMBER=&EMAIL=#################&PAYERID=&PAYERSTATUS=&BUSINESS=&SALUTATION=&FIRSTNAME=Tom+Company&MIDDLENAME=&LASTNAME=Tom+Company&SUFFIX=&STREET=Kolkata&STREET2=&CITY=Kolkata&STATE=West+Bengal&COUNTRYCODE=IN&ZIP=700001&PHONENUM=&SHIPTONAME=&SHIPTOSTREET=&SHIPTOSTREET2=&SHIPTOCITY=&SHIPTOSTATE=&SHIPTOZIP=&SHIPTOCOUNTRY=&SHIPTOPHONENUM=
[RAWRESPONSE] =>
）
这背后的原因是什么？