subscribe query and publish - how?

[pw44]

I'm trying the following:

subscribe to a topic
by paylod make a query to a database
publish to another topic.

`
mqtt = new Bluerhinos\phpMQTT($server, $port, $client_id);
if(!$mqtt->connect(true, NULL, $username, $password)) {
echo "Failed to connect to Mqtt: ";
exit(1);
}

$con = new mysqli($mysql_host, $mysql_user, $mysql_pass, $mysql_mydb );
if ($con -> connect_errno) {
echo "Failed to connect to MySQL: " . $con -> connect_error;
exit(2);
}
$con->set_charset('utf8mb4'); // always set the charset

$mqtt->debug = true;

$topics['rfid/card/ping'] = array('qos' => 0, 'function' => 'procMsg');
$mqtt->subscribe($topics, 0);
while($mqtt->proc()) {
// echo "proc.....";
}
$mqtt->close();

function procMsg($topic, $msg){
echo 'Msg Recieved: ' . date('r') . "\n";
echo "Topic: {$topic}\n";
echo "Payload: {$msg}\n";
echo $msg;
echo "\n";
// query con
//$tagid = "39EAB06D";
$query = "SELECT name, id FROM rfidtags WHERE id = ?";
$stmt = $con->prepare($query);
$stmt->bind_param('s', $msg);
$stmt->execute();
$stmt->store_result();
$stmt->bind_result($name, $id);
if ($stmt->fetch()) {
echo "$name $id\n";
echo "1";
} else {
echo "failed to fetch data\n";
echo "2";
}
$con->close();
}
`

but the error:

paulo@hp15pw:~/TOOLS/MQTT-PHP$ php subscribe-query-publish.php
Mon, 19 Jul 2021 12:22:32 -0300: Received CMD: 3 (PUBLISH)
Mon, 19 Jul 2021 12:22:32 -0300: Fetching: 24 bytes
Msg Recieved: Mon, 19 Jul 2021 12:22:32 -0300
Topic: rfid/card/ping
Payload: 39EAB06D
39EAB06D
PHP Notice: Undefined variable: con in /home/paulo/TOOLS/MQTT-
PHP/subscribe-query-publish.php on line 51
PHP Fatal error: Uncaught Error: Call to a member function prepare() on
null in /home/paulo/TOOLS/MQTT-PHP/subscribe-query-publish.php:51
Stack trace:
#0 [internal function]: procMsg()
#1 /home/paulo/TOOLS/MQTT-PHP/phpMQTT.php(482): call_user_func()
#2 /home/paulo/TOOLS/MQTT-PHP/phpMQTT.php(547): Bluerhinos\phpMQTT-

message()
#3 /home/paulo/TOOLS/MQTT-PHP/subscribe-query-publish.php(36):
Bluerhinos\phpMQTT->proc()
#4 {main}
thrown in /home/paulo/TOOLS/MQTT-PHP/subscribe-query-publish.php on line 51

any clue?

[anhlephuoc]

The $con variable you used in the procMsg() function is a local version because it is undeclared. An uninitialised $con is used.
If you want to refer to the GLOBAL version of the $con you initialised earlier, then you should declare as such in the function procMsg().

[pw44]

hi, thx for answering.

solved it in a much easier way:

`
<?php

 require('phpMQTT.php');


 $server = 'hp15pw';     // change if necessary
 $port = 1883;                     // change if necessary
 $username = 'mqttuser';                   // set your username
 $password = 'mqttpass';                   // set your password
 $client_id = 'phpMQTTDB'; // make sure this is unique for connecting to sever - you could use uniqid()

 $mysql_host = 'localhost';
 $mysql_port = '';
 $mysql_user = 'dbuser';
 $mysql_pass = 'dbpass';
 $mysql_mydb = 'rfidcards';

 $mqtt = new Bluerhinos\phpMQTT($server, $port, $client_id);
 if(!$mqtt->connect(true, NULL, $username, $password)) {
   echo "Failed to connect to Mqtt: ";
   exit(1);
 }


 $con = new mysqli($mysql_host, $mysql_user, $mysql_pass, $mysql_mydb );
 if ($con -> connect_errno) {
     echo "Failed to connect to MySQL: " . $con -> connect_error;
     exit(2);
  }
 $con->set_charset('utf8mb4'); // always set the charset

 //$mqtt->debug = true;

 while (true) {

       $msg = $mqtt->subscribeAndWaitForMessage('rfid/card/ping', 0);
       echo "$msg";

       // query con
       //$tagid = "39EAB06D";
       $query = "SELECT name, id  FROM rfidtags WHERE id = ?";
       $stmt = $con->prepare($query);
       $stmt->bind_param('s', $msg);
       $stmt->execute();
       $stmt->store_result();
       $stmt->bind_result($name, $id);
       if ($stmt->fetch()) {
            echo "$name $id\n";
           $pong="1";
       } else {
           echo "failed to fetch data\n";
           $pong= "2";
       }
       $mqtt->publish('rfid/card/pong', "$pong", 0, false);

   }

  $con->close(); 
  $mqtt->close();

`

[anhlephuoc]

The problem here is with your own basic PHP coding. Nothing to do phpMQTT code.
You have received a suggestion for fixing you program; and you also have your own fix.
May be it's time to close the issue!. No body else can fix your own code for you.