Overview:

Dompdf is an HTML to PDF converter written in PHP that is CSS 2.1 compliant. It is a style-driven renderer that can handle external stylesheets, inline styles, and presentational HTML attributes. It is capable of rendering complex tables, supporting various image formats, and does not require external PDF libraries.

Features:

CSS Support: Handles most CSS 2.1 and a few CSS3 properties like @import, @media, and @page rules.
HTML Attributes: Supports presentational HTML 4.0 attributes.
External Stylesheets: Supports external stylesheets through local files or http/ftp.
Table Support: Capable of rendering complex tables with row & column spans and individual cell styling.
Image Support: Supports various image formats like gif, png, bmp, and jpeg.
No Dependencies: Does not rely on external PDF libraries.
Font & Character Encoding: Supports fonts like Helvetica, Times-Roman, Courier, Zapf-Dingbats, and Symbol internally.

Install with Composer:

composer require dompdf/dompdf

Download and Install:

Download a packaged archive of dompdf.
Extract it into the directory where dompdf will reside.

Requirements:

PHP version 7.1 or higher
DOM extension
MBString extension
php-font-lib
php-svg-lib
Additional recommendation: GD extension for image processing

For full installation details, including dependencies and recommendations, visit the Dompdf wiki page.

Summary:

Dompdf is a CSS 2.1 compliant HTML to PDF converter written in PHP. It offers extensive support for CSS properties, HTML attributes, and complex tables. The tool does not depend on external PDF libraries and provides options for external stylesheets and font embedding for varied character encoding support. Installation can be done either via Composer or by downloading and extracting the packaged archive, adhering to the specified PHP version and extensions requirements.