Troubleshooting

Headers already sent

Sometimes the following error message is found in the php log or in the output:

Warning:

PHP Warning: Cannot modify header information - headers already sent by...

This usually occurs when there has already been sent content to the output buffer before the pdf fluid template is rendered. Since we need to set some headers in order to allow the browser to interpret the content as pdf file for inline display / download, pdfviewhelpers need to be able to set headers, and this can only be done if there was no output at all on that page before the pdf is rendered.

PDF does not validate

Sometimes, the generated pdf does not correctly validate e.g. in https://www.pdf-online.com/osa/validate.aspx If this is the case, check the generated file in a text editor, especially the end of the file. Ensure there is no content after the %%EOF.

If you want to have a valid PDF/A document, validate the xml in the metadata in the

Code:

<< /Type /Metadata /Subtype /XML /Length 4505 >> stream
<?xpacket begin="Ôªø" id="W5M0MpCehiHzreSzNTczkc9d"?>
<x:xmpmeta xmlns:x="adobe:ns:meta/" x:xmptk="Adobe XMP Core 4.2.1-c043 52.372728, 2009/01/18-15:08:04">
    <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
        ...
        </rdf:Description>
    </rdf:RDF>
</x:xmpmeta>
<?xpacket end="w"?>

Section with e.g. here: https://www.w3schools.com/xml/xml_validator.asp

Also ensure you have disabled all html header output:

pdfpage = PAGE
pdfpage {
	10 = FLUIDTEMPLATE
	10 {
		file = EXT:pdfviewhelpers/Resources/Public/Examples/BasicUsage/Template.html
	}
	# ensure there is no other output apart from the pdf
	# take a look at the generated pdf file (end!) in a text editor to verify there is no other output
	# like warnings, error messages or html code
	config {
		disableAllHeaderCode = 1
		xhtml_cleaning = 0
		admPanel = 0
	}
}

pdfviewhelpers can not be installed via TER

The extension pdfviewhelpers is quite big compared to other extensions, as it ships with the entire TCPDF in order to be easily installable via TER. The size EXT:pdfviewhelpers might be an issue if your memory_limit or max_execution_time is quite low, try increasing these values.

PHP

ini_set('max_execution_time', 300);
ini_set('memory_limit', '512M');

php.ini

max_execution_time = 300
memory_limit = 512M