如何在变量中保存foreach循环值并将其打印到循环外？

Question

I am trying to email a student list. Student list data saved already in a database.

So I created a query to retrieve the data according to the merchTxnRef

then retriveing the row from the table/record and assign it to a variable..

and then concatenate the variable to the mail body and trying to send them.

but my <tr></tr> is empty in the mail.. I know it is because of I am saving the foreach loop variable incorrectly to this variable $studentList

how can I save the foreach loop values in a variable and print it outside of the loop

Following is the code I am trying.

$sqlListst = "SELECT * FROM tck_paymentStudents WHERE merchTxnRef LIKE $merchTxnRef'";

$resultListst = $wpdb->get_results($sql) or die(mysql_error());

foreach( $resultListst as $resultsListst ) {

        $merchTxnRef = $resultsListst->merchTxnRef;
        $sudentname = $resultsListst->sudentname;
        $admissionnmbr = $resultsListst->admissionnmbr;
        $purpose = $resultsListst->purpose;
        $amount = $resultsListst->amount;
        $grade = $resultsListst->grade;

        $studentList = '<tr><td>'.$merchTxnRef.'</td><td>'.$sudentname.'</td><td>'.$admissionnmbr.'</td><td>'.$purpose.'</td><td>'.$amount.'</td><td>'.$grade.'</td></tr>';
}
    $mail_body_guest_full  = '<table>';
    $mail_body_guest_full .=  $studentList;
    $mail_body_guest_full .= '</table>';

    $email = '[e-mail]';
    $subject = 'Student List';
    $from_guest = '[e-mail]';
    $headers_guest = array('From: My Site <'.$from_guest.'>');

    $mail_sent_guest = wp_mail( $email, $subject, $mail_body_guest_full, $headers_guest );

Answer 1

1) Missing concatination dot near $studentList.=

2) Missing single quotes in query near LIKE '".$merchTxnRef."'";

3) As per your comment $wpdb->get_results($sqlListst)

      $sqlListst = "SELECT * FROM tck_paymentStudents WHERE merchTxnRef LIKE '".$merchTxnRef."'";
      $resultListst = $wpdb->get_results($sqlListst) or die(mysql_error());
       foreach( $resultListst as $resultsListst ) 
       {
        $merchTxnRef = $resultsListst->merchTxnRef;
        $sudentname = $resultsListst->sudentname;
        $admissionnmbr = $resultsListst->admissionnmbr;
        $purpose = $resultsListst->purpose;
        $amount = $resultsListst->amount;
        $grade = $resultsListst->grade;

        $studentList.= '<tr><td>'.$merchTxnRef.'</td><td>'.$sudentname.'</td><td>'.$admissionnmbr.'</td><td>'.$purpose.'</td><td>'.$amount.'</td><td>'.$grade.'</td></tr>';
       }
        $mail_body_guest_full  = '<table><tbody>';
        $mail_body_guest_full .=  $studentList;
        $mail_body_guest_full .= '</tbody></table>';

        $email = '[e-mail]';
        $subject = 'Student List';
        $from_guest = '[e-mail]';
        $headers_guest = array('From: My Site <'.$from_guest.'>');

        $mail_sent_guest = wp_mail( $email, $subject, $mail_body_guest_full, $headers_guest );