sum of amount in all mysql table names from array

I have 6 mysql tables in my database.

and each table contains column 'amount'

I want sum of all amounts in all tables.

But getting error as

 Invalid argument supplied for foreach() in //  foreach ($tablenames as $tablename) {

and

 undefined variable query

Code is as follows :

I want specific tables from my database and more tables will be added per year which will contain amount column. So I extracted table names first.

$tablenamearray = array(); 
    
$tablenamequery = "SELECT table_name FROM information_schema.tables WHERE table_schema = 'databasename' and table_name LIKE '%registration%'";

$tablenameres = $database->get_results($tablenamequery);
foreach ($tablenameres as $tablenamedata){
    $tablenamearray[]=$tablenamedata['table_name'];
}

$tablenamearray_final =   "'".join("', '",$tablenamearray)."'"; 
$tablenamesrcvd = "array(".$tablenamearray_final.");";

///$tablenamesrcvd are as given below when I echo
// array('table_1','table_2','table_3','table_4','table_5','table_6'); 

foreach ($tablenamesrcvd as $tablename) {
    $query = "select SUM(`amount`) as Total from $tablename";
    $res = $database->get_results($query); // using wrapper class
    foreach ($res as $data){
        $totalrcvd = $data['Total'];
    }       
}

What I am missing ?

Answer

$tablenamesrcvd is a string, not an array.

The variable $tablenamearray contains the array of table names, you can loop over that. You don’t need to convert it to a string.

You should also add to $totalrcvd, not reassign it each time through the loop, using += instead of =.

$totalrcvd = 0;
foreach ($tablenamesarray as $tablename) {
    $query = "select SUM(`amount`) as Total from $tablename";
    $res = $database->get_results($query); // using wrapper class
    foreach ($res as $data){
        $totalrcvd += $data['Total'];
    }       
}
echo $totalrcvd;