无法将php应用程序连接到AWS rds实例

I am trying to connect my PHP application to AWS rds. I have done all the steps and finally when i write the connection like this:

$link = mysqli_connect($_SERVER['amazon-endpoint'], $_SERVER['myMasterUserName'], $_SERVER['myMasterUserPassword'], $_SERVER['ebdb'], $_SERVER['3306']);
if(mysqli_connect_errno()){
die("database connection failed: " . mysqli_connect_error() . " (" .
mysqli_connect_errno() . ")");
}

I get this error: database connection failed: No such file or directory (2002)

First Create a security group which allows your public ip to RDS instance. The check you could connect to RDS Db using mysql command line Then

$con = mysqli_connect("yourAmazonEndPoint","UserName","Password","your_db");

check this for security groups

from console :

mysql -h myinstance.123456789012.us-east-1.rds.amazonaws.com -P 3306 -u mymasteruser -p

or

mysql -h myinstance.123456789012.us-east-1.rds.amazonaws.com --ssl-ca=rds-ca-2015-root.pem