PHP Mysqli数据库连接池，以避免最大用户数

I surfed on Internet for past two days to create the DB pooling by PHP, but not yet achieved. I'm using PHP and MySQLi. We bought the mysqli db with 15 Maximum user connection. I want to pool the db connection to avoid the new connection. I used persistent as well as mysqli_connect. but I don't feel much different both are creating the new connection since other user already logged in. I was trying this function to get DB connection.

 <?php
function getConnection(){
    if ($connect){
        return $connect;
    }else{
        $connect = new mysqli('p:xxxx','yyy','zzz','aaaa');
        return $connect;
        if(mysqli_connect_errno($connect))
        {
            echo "Server Busy";
        }
    }
}
 ?>

But above function only returns the else part. Please suggest me how to handle this. Thanks in advance. For now I'm killing the process which are in sleep mode to reduce the probability of increasing DB connection.

This is not how it works. See here. MySQLi will select one of available connections when you execute new mysqli('p:... The connection is persistent, not the PHP object.

function getConnection(){
    mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
    return (new mysqli('p:xxxx','yyy','zzz','aaaa'));
}