$key= 'NO9pn4tMn3aIvwX95CyxFlFzexXmzOFp';
$secret= 'xNBf8CcKJW1GImCiVt1LHWFb68hDOLcARrNA5rTCACY=';
序列化请求参数：
$json = json_encode([
    "outerTradeNo"    =>"D202410010000000004",
    "realName"    =>"凌小云",
    "phone"    =>"17666666666",
    "idCard"    =>"50000000000",
    "idCardType"=>1,
    "payAccount"    =>"17666666666",
    "reason"    =>"推广费用",
    "balance"=>5.20,
    "bizAccount"=>"13888888888",
    "taskId"=>1,
],JSON_UNESCAPED_UNICODE);
json: 
{"outerTradeNo":"D202410010000000004","realName":"凌小云","phone":"17666666666","idCard":"50000000001","idCardType":1,"payAccount":"17666666666","reason":"推广费用","balance":5.2,"bizAccount":"13888888888","taskId":1}
php加密代码:
$iv = "0000000000000000"
$encrypt = openssl_encrypt($json, 'AES-256-CBC', base64_decode($secret), OPENSSL_RAW_DATA, $iv);  
echo base64_encode($encrypt); 
加密后：
zzMvuQIn8wD5wV68jRvJEimnoLrCMumVIUDcRukB2bAc8rAGIQSv1WzT8tJ7JrYVbmxQuF+iQB5yMt1HNBFCPVe0ZdWxgwto1LV0lgju5vfKBJrcA8KbW6b23E6OgIo66K98GJYGqLIN7XRoi1FQ37KpKfVDb6KehZ8GCiDC7i6phwfwsd3HUka1skaGuaWOa5enFQky23Hr/GItpX1ORtz5pRzolKbIqb2UKEITZggPUREk4f3RyoGd0bQPMUbKcWLCgIY/uoo04imaLJiDZopzEfS6Nut9Aoq7f593g2Fp8GhgyRYm5aS/ZaK0UMqt
解密密后：
{"outerTradeNo":"D202410010000000004","realName":"凌小云","phone":"17666666666","idCard":"50000000001","idCardType":1,"payAccount":"17666666666","reason":"推广费用","balance":5.2,"bizAccount":"13888888888","taskId":1}