Uncaught Mpdf\MpdfException: данные уже отправлены на вывод ⇐ Php

[Гость]

I am trying to use mPDF library on my wordpress (wp-admin) but i am getting this error:

Fatal error: Uncaught Mpdf\MpdfException: Data has already been sent to output (\wp-includes\script-loader.php at line 2925), unable to output PDF file

so this is the WordPress function i have written

function display_student_details() { // Check if student ID is provided in the query string if (isset($_GET['id'])) { $student_id = intval($_GET['id']); // Get student ID from the query string // Start output buffering ob_start(); global $wpdb; // Fetch student details from the database $student_details = $wpdb->get_row( $wpdb->prepare("SELECT id, firstName, secondName FROM wrbc_studentReg WHERE id = %d", $student_id), ARRAY_A ); if ($student_details) { // Prevent WordPress from sending additional content if (ob_get_length()) { ob_end_clean(); } // Set up Mpdf require_once __DIR__ . '/mpdf/vendor/autoload.php'; // Create new PDF document $mpdf = new \Mpdf\Mpdf(); // Add content to PDF $mpdf->WriteHTML('Student Details'); foreach ($student_details as $key => $value) { $mpdf->WriteHTML("{$key}: {$value}
"); } // Output PDF $mpdf->Output('student_details.pdf', 'I'); exit; // Stop execution after generating PDF ob_end_clean(); } else { echo '
No details found for the selected student.
'; } } else { echo '
No student ID provided.
'; } }
I tried to follow the solution from this stackoverflow question by using ob_end_clean but in vain.