如何用Mpdf覆盖pdf？

Question

我有一个pdf文件格式现在我想用其他文本替换一些文本。我尝试了一些解决方案但不适合我。这是代码

$this->load->library('m_pdf');
        $mpdf = $this->m_pdf->load();
        $mpdf->SetImportUse();
        $mpdf->simpleTables = true;
        $mpdf->packTableData = true;
        $mpdf->percentSubset = 0;
        $search = array("student_name");
        $replacement = array("abc");

        $student_format = dirname(APPPATH)."/format/student.pdf";

        $mpdf->OverWrite($student_format, $search, $replacement, 'F', 'new.pdf' ) ;

        die();