To generate PDFs in PHP, you can use a library like TCPDF or FPDF. Here's an example using TCPDF:

1) First, make sure you have TCPDF library installed. You can download it from the official website (https://tcpdf.org/) and extract it to your project directory.

2) Create a new PHP file, e.g., pdf_generator.php, and include the TCPDF library:

3) Define your PDF generation logic within the PHP file. Here's a simple example that generates a PDF with some text content : 

In this example, we create a new TCPDF instance and set the document information. We add a page, set the font, and add some content to the PDF. Finally, we output the PDF as a file with the name "sample.pdf" and the "D" option to force a download.

4) Access the pdf_generator.php file in your browser, and it should trigger the download of the generated PDF file. 

You can further customize the PDF generation by exploring the TCPDF documentation and its available methods and options.