You can also try my project here. It provides a clean OO interface to the command line utility:
https://github.com/mikehaertl/phpwkhtmltopdf
Usage is very simple:
<?php
use mikehaertl\wkhtmlto\Pdf;
$pdf = new Pdf;
// Add a HTML file, a HTML string or a page from a URL
$pdf->addPage('/home/joe/page.html');
$pdf->addPage('<html>....</html>');
$pdf->addPage('http://google.com');
// Add a cover (same sources as above are possible)
$pdf->addCover('mycover.html');
// Add a Table of contents
$pdf->addToc();
// Save the PDF
$pdf->saveAs('/tmp/new.pdf');
// ... or send to client for inline display
$pdf->send();