ClibPDF is an open source

Open source

The term open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology...

 library

Library (computer science)

In computer science, a library is a collection of resources used to develop software. These may include pre-written code and subroutines, classes, values or type specifications....

 which allows the programmer to create dynamically-generated PDF

Portable Document Format

Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....

 files directly from within a program's code. Such applications include use in PHP

PHP

PHP is a general-purpose server-side scripting language originally designed for web development to produce dynamic web pages. For this purpose, PHP code is embedded into the HTML source document and interpreted by a web server with a PHP processor module, which generates the web page document...

. While ClibPDF was once the defacto standard for dynamic PDF generation, according to "ClibPDF support is deprecated and users are strongly encouraged to use an alternative, like Haru, PDFlib, or one of the available PHP alternatives."