Easy PDF Generation in PHP

Introduction

PDF is a popular, versatile format for storing content. PDF
files can be generated once, and distributed in peace knowing that they
will look the same across all platforms. They also serve as a perfect
way of allowing your users to download or email a page from your
website. In this tutorial, I’ll show you how to generate PDF files in
pure PHP and distribute your content in a single, consistent format.

Ever wanted to generate PDF files in your web application? You could
let your users download pages in PDF format, generate PDF reports to be
distributed in your organisation, or just get better control over how
your pages look when printed. In this PHP PDF tutorial, we’ll work through
building a simple page and saving it as a PDF file.

We’ll be using the FPDF library
to generate our PDF files. The library is a simple PHP class that
provides some very complex PDF generation functionality. Luckily, it
offers some high level methods that you can use to quickly and easily
generate PDF files without having to understand the internals of the
PDF format.

Why would you want to generate PDFs?

When it comes to data output (not interface, output), web
applications face an inherent problem: complex format and structures
are very unreliable. For your complex reporting interfaces, you are
faced with browser compatibility challenges, screen width issues and
font size uncertainty. When it comes to demoing your latest version to
your client, you may often find yourself embarassed by unforseen
environment issues, and it’s hard to tell a client their computer is
broken.

At the same time, distributing reports – or any content, for that
matter – from your web applications is also tricky. Users can try the
"Save As" or "Save Page As" function in their browser, which will then
attempt to calculate all the file dependencies and create an
independent copy of the current page. Users will often distribute only
the HTML page, losing all the CSS files and images – and with it, all
hope of the end user viewing your data.

PDF as a format solves these problems wonderfully. When it comes to
laying out a PDF document, you can simply assume it will look the same
on your system as on the end user’s. Screen resolution differences?
Adobe Reader will scale beautifully. Images? SVG them and you’ll have
no problems; photographic data can cleanly resize. Browser versions? As
long as they’re all using Adobe Reader, or a reasonable alternative
(such as Foxit Reader), you’re fine.

Think of it like web design in a world where everyone uses Firefox.

Options for PDF Generation

In this article, we’ll take a look at FPDF. However, you may have noticed a section in the PHP manual itself with PDF functions. A brief look at php.net/pdf reveals a PDFLib-based PECL extension
that has not been updated in nearly six months. PDFLib itself is not
free, however, and PDFLib Lite is not terribly effective. You also need
access to the server to install the extension, which isn’t always
possible on a shared host.

There is a special section in the PHP manual on this – take a look at this FAQ entry. The two main free alternatives to FPDF are the R&OS PDF Class and phppdflib, but neither have been updated in a few years. There’s also the Zend_PDF component of the Zend Framework,
although it isn’t very mature – still worth a look if you use the Zend
Framework, however. In this time, FPDF has become the de facto standard
for PDF generation in PHP. Other options exist – such as using COM to
communicate with an existing Windows application with PDF export
functionality – however none are as reliable and flexible as FPDF. In
this tutorial, we’ll be using FPDF exclusively, but the alternatives
are definitely worth a look, especially their source code.

Hello World with FPDF

Let’s get started with some basic PDF generation using FPDF. Load up your code editor and bash out the following:

<?php
require('fpdf.php');
$PDF = new FPDF();

$PDF->AddPage();
$PDF->SetFont('Arial', 'B', 16);
$PDF->Cell(40, 10, 'Hello World!');

$PDF->Output();

I’ll explain what all this does in a moment. For now, grab the latest version of FPDF from fpdf.org, extract it to somewhere in your web server’s document root and save this snippet in a PHP file under the same folder as fpdf.php. Load it up in your web browser and you should see something like this:

Nothing special, but we’re on our way to PDF glory!

Examining the code

Let’s take a look through that Hello World! snippet we just wrote.

<?php
require('fpdf.php');
$PDF = new FPDF();

$PDF->AddPage();
$PDF->SetFont('Arial', 'B', 16);
$PDF->Cell(40, 10, 'Hello World!');

$PDF->Output();

Barring the output, this is pretty standard stuff. Here’s a quick rundown.

We start by including the FPDF library with the require('fpdf.php')
line. FPDF is pure PHP: that is, no PECL extension is required. It’s a
little slower than PDFLib and CPDFLib, but it’s infinitely more
portable and much easier to use.

We create a new instance of the FPDF class in $PDF.
Typically, for each PDF document you want to work with (each document
can have multiple pages), you’ll want to use a new object. Chances are,
however, that you’ll only ever need one.

This is where we launch into the actual PDF construction. We first
need to create a page. That’s right – you can have a PDF document with
no pages. If you omit the AddPage() call and the
subsequent two lines, then try it in your browser, Adobe Reader will
display a blank empty page, but there really isn’t one. As an example,
let’s take a look at what the library outputs without any pages, fonts
or text cells created:

%PDF-1.3

3 0 obj

<</Type /Page

/Parent 1 0 R

/Resources 2 0 R

/Contents 4 0 R>>

endobj

4 0 obj

<</Filter /FlateDecode /Length 19>>

stream

x�3R��2�35W(�

Nothing terribly spectacular, especially consider its an empty document.
However, this is a barebones PDF document, and while you may never have
to actually work with this, it’s important to be aware of what’s
happening. As this is all purely text, all the Output() method (which we’ll examine in a moment) does is send a HTTP header of application/pdf and print this data to the page.

But back to our code. Here’s the bulk of our PDF:

$PDF->AddPage();
$PDF->SetFont('Arial', 'I', 14);
$PDF->Cell(40, 10, 'Hello World!');

This tells FPDF to first create a page within our PDF document (it
works with an internal copy while constructing your PDF), then set the
font currently in use to italicised Arial at 14pt. If you don’t set a
font, it will default to no font and your text will not display as part
of the PDF.

Finally, we create a text cell on the page, with a width of 40 and height of 10, and write the text ‘Hello World!’ in it. The Cell()
method is the workhorse of the FPDF library. A cell is a rectangular
area with optional borders, background colour and character string.
Whenever you want to print text to your PDF file, chances are you’ll be
using the Cell() method. The method has eight arguments,
even though we’ve only supplied three here. The others include a border
option, text alignment, transparent or filled background and URL – read
this manual page on the Cell method for further information.

The Output() method is especially interesting. By
default it will output the PDF file as the current web page (or shell),
but it can also save your newly generated PDF file to disk. To save to
disk, for example, we would call the method with $PDF->Output('output.pdf', 'F').
In the first argument, we specify the file name to output (typically
relative to the directory of the current script, not the FPDF library
file). In the second, we specify ‘F’ for File, to save to a local file.
Other options include sending inline to the browser (default), forcing
the browser to download the file, or even simply returning the document
data as a string. See this manual page for more details on the options available.