我也遇到了同样的问题。解决方案是codeigniter pdf库$this->load->library（'pdf'）;创建一个DOMPDF示例，每次都调用它，但是这个类不能正确地清理它自己，所以如果你需要生成多个pdf，它会崩溃。
解决方案是根据需要手动示例化DOMPDF类。不要使用codeigniter pdf Package 器。

//require at the top of our script
require_once(APPPATH .'libraries/dompdf/dompdf_config.inc.php');

//get the html first (base dompdf cant do the combined load/render)
$view = $this->load->view("viewname", $viewData, true);
//create a new dompdf instance (this is the crucial step)
$this->pdf = new DOMPDF();
//render and output our pdf
$this->pdf->load_html($view);
$this->pdf->render();
$pdf = $this->pdf->output(array("compress" => 0));
file_put_contents("some/file/path.pdf", $pdf );

当我试图在循环中生成pdf时，我遇到了CodeIgniter 3的这个问题。问题是由于多次加载pdf库而未清除现有示例。为了避免这种情况-我每次都创建了新的PDF示例。

require_once APPPATH.'third_party/dompdf/autoload.inc.php';
use Dompdf\Dompdf;

class Index extends CI_Controller {

    public function gencert() {
       $nurseids = $this->nurse_model->getNurseIdsForCert();
       foreach($nurseids as $nid){
         //print_r($nid);
         $this->nursecertificate($nid->nurseid);
       } 
    }
    
    private function nursecertificate($nurseid){
       // Load pdf library
       //$this->load->library('pdf');
       $this->pdf = new DOMPDF();
    
       // Load HTML content
       $this->pdf->loadHtml($html, []);
       ...