dompdf is an HTML to PDF converter. At its heart, dompdf is (mostly) a CSS 2.1 compliant HTML layout and rendering engine written in PHP. It is a style-driven renderer: it will download and read external stylesheets, inline style tags, and the style attributes of individual HTML elements. It also supports most presentational HTML attributes.

PDF rendering is currently provided either by PDFLib or by a bundled version the R&OS CPDF class written by Wayne Munro. (Some important changes have been made to the R&OS class, however). In order to use PDFLib with dompdf, the PDFLib PECL extension is required. Using PDFLib improves performance and reduces the memory requirements of dompdf somewhat, while the R&OS CPDF class, though slightly slower, eliminates any dependencies on external PDF libraries.

Features

Handles most CSS 2.1 and a few CSS3 properties, including @import, @media & @page rules
Supports most presentational HTML 4.0 attributes
Supports external stylesheets, either local or through http/ftp (via fopen-wrappers)
Supports complex tables, including row & column spans, separate & collapsed border models, individual cell styling
Image support (gif, png (8, 24 and 32 bit with alpha channel), bmp & jpeg)
No dependencies on external PDF libraries, thanks to the R&OS PDF class
Inline PHP support
Basic SVG support

Requirements

PHP version 7.1 or higher
DOM extension
MBString extension
php-font-lib
php-svg-lib

Note that some required dependencies may have further dependencies (notably php-svg-lib requires sabberworm/php-css-parser).

Recommendations

OPcache (OPcache, XCache, APC, etc.): improves performance
GD (for image processing)
IMagick or GMagick extension: improves image processing performance

Visit the wiki for more information: https://github.com/dompdf/dompdf/wiki/Requirements

Limitations (Known Issues)

Dompdf is not particularly tolerant to poorly-formed HTML input. To avoid any unexpected rendering issues you should either enable the built-in HTML5 parser at runtime ($dompdf->set_option('isHtml5ParserEnabled', true);) or run your HTML through a HTML validator/cleaner (such as Tidy or the W3C Markup Validation Service).
Table cells are not pageable, meaning a table row must fit on a single page.
Elements are rendered on the active page when they are parsed.