据我所知,您收到的错误不是由您在问题中发布的代码引起的,因为该代码是直截了当的,并且与 TCPDF 文档中的代码完全相同。您可以在TCPDF 文档中找到发送签名 pdf 的示例
那里的代码如下:
require_once('../config/lang/eng.php');
require_once('../tcpdf.php');
// create new PDF document
$pdf = new TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
// set document information
$pdf->SetCreator(PDF_CREATOR);
$pdf->SetAuthor('Nicola Asuni');
$pdf->SetTitle('TCPDF Example 052');
$pdf->SetSubject('TCPDF Tutorial');
$pdf->SetKeywords('TCPDF, PDF, example, test, guide');
// set default header data
$pdf->SetHeaderData(PDF_HEADER_LOGO, PDF_HEADER_LOGO_WIDTH, PDF_HEADER_TITLE.' 052', PDF_HEADER_STRING);
// set header and footer fonts
$pdf->setHeaderFont(Array(PDF_FONT_NAME_MAIN, '', PDF_FONT_SIZE_MAIN));
$pdf->setFooterFont(Array(PDF_FONT_NAME_DATA, '', PDF_FONT_SIZE_DATA));
// set default monospaced font
$pdf->SetDefaultMonospacedFont(PDF_FONT_MONOSPACED);
//set margins
$pdf->SetMargins(PDF_MARGIN_LEFT, PDF_MARGIN_TOP, PDF_MARGIN_RIGHT);
$pdf->SetHeaderMargin(PDF_MARGIN_HEADER);
$pdf->SetFooterMargin(PDF_MARGIN_FOOTER);
//set auto page breaks
$pdf->SetAutoPageBreak(TRUE, PDF_MARGIN_BOTTOM);
//set image scale factor
$pdf->setImageScale(PDF_IMAGE_SCALE_RATIO);
//set some language-dependent strings
$pdf->setLanguageArray($l);
// ---------------------------------------------------------
/*
NOTES:
- To create self-signed signature: openssl req -x509 -nodes -days 365000 -newkey rsa:1024 -keyout tcpdf.crt -out tcpdf.crt
- To export crt to p12: openssl pkcs12 -export -in tcpdf.crt -out tcpdf.p12
- To convert pfx certificate to pem: openssl pkcs12 -in tcpdf.pfx -out tcpdf.crt -nodes
*/
// set certificate file
$certificate = 'file://../config/cert/tcpdf.crt';
// set additional information
$info = array(
'Name' => 'TCPDF',
'Location' => 'Office',
'Reason' => 'Testing TCPDF',
'ContactInfo' => 'http://www.tcpdf.org',
);
// set document signature
$pdf->setSignature($certificate, $certificate, 'tcpdfdemo', '', 2, $info);
// set font
$pdf->SetFont('helvetica', '', 12);
// add a page
$pdf->AddPage();
// print a line of text
$text = 'This is a <b color="#FF0000">digitally signed document</b> using the default (example) <b>tcpdf.crt</b> certificate.<br />To validate this signature you have to load the <b color="#006600">tcpdf.fdf</b> on the Arobat Reader to add the certificate to <i>List of Trusted Identities</i>.<br /><br />For more information check the source code of this example and the source code documentation for the <i>setSignature()</i> method.<br /><br /><a href="http://www.tcpdf.org">www.tcpdf.org</a>';
$pdf->writeHTML($text, true, 0, true, 0);
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// *** set signature appearance ***
// create content for signature (image and/or text)
$pdf->Image('../images/tcpdf_signature.png', 180, 60, 15, 15, 'PNG');
// define active area for signature appearance
$pdf->setSignatureAppearance(180, 60, 15, 15);
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// *** set an empty signature appearance ***
$pdf->addEmptySignatureAppearance(180, 80, 15, 15);
// ---------------------------------------------------------
//Close and output PDF document
$pdf->Output('example_052.pdf', 'I');
请注意,您需要将页面添加到文档中,然后调用 Output() 函数才能实际获取发送到浏览器的任何输出。否则,服务器将没有任何数据要发送,因此会给您一个空响应,从而导致此错误。
如果您在服务器上创建文件并将其保存在您的脚本没有权限访问和输出到浏览器的文件夹中,也可能导致此错误。
如果您使用 Google Chrome 查看您的 pdf,您可能需要在此处查看有关此错误的信息Chrome Empty Response Errors Group
此外,有报告称此错误是由错误配置的 Zend Optimizer/Zend Guardian 设置引起的。如果上述两种情况都不是,我会确保这些都已停用以继续进行故障排除。
如您所见,此错误有点不具体,因此很难排除故障。