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FOML for PHP

What is FOML?

Format Objects Markup Language (FOML) is a concise language for PDF document layout. This library provides a framework for converting FOML into XLS-FO, and bindings to Apache FOP to render the output as a PDF document.

FOML gives you a concise and powerful way to generate PDF reports, and isolates the layout from your application logic. It keeps the PDF layout logic the hell off your application's lawn.

The good parts of FOML were stolen from HAML. See the original blog post about FOML for more background.

Installation

  1. Clone the FOML repository into your PHP code library.

  2. Download the binaries (compiled Java, but they call them binaries) for FOP from The Apache FOP site.

wget http://mirror.mel.bkb.net.au/pub/apache/xmlgraphics/fop/binaries/fop-1.1-bin.zip
  1. Untar the FOP binaries into a subdirectory inside the FOML directory.
unzip fop-1.1-bin.zip
chmod ugo+x fop-1.1/fop
rm fop-1.1-bin.zip
  1. Install Java if you don't already have it, and verify that the fop executable will launch okay from the command line. fop-1.1/fop -version should generate a version number.
%fop-1.1/fop -version
FOP Version 1.1

Your installation will have a directory structure something like this:

  +-application/
    +--FOML/
       +--.fop/
       +--examples/
          +--foml/
       +--fonts/
       +--fop-1.1/
          +--fop    (this is a shell script that launches fop)

Fonts

FOML supports custom TTF fonts and embedding fonts in PDF files. One important consideration when using custom fonts is setting file permissions to ensure that the font cache can be saved, since Fop will generally be run in the context of the web server, running as user httpd or www for example.

The steps for adding custom fonts are:

  1. Download your font to FOML/fonts.

  2. Ensure that FOML/.fop is writable by the http user.

  3. Uncomment the following lines in fop.xconf:

<directory>fonts</directory>
<auto-detect/>
  1. Reference your font in FOML like this: %block(font-family="Droid Sans")

By default any custom fonts you download will be embedded in the generated PDF. When using TTF fonts, only the glyphs actually used will be embedded.

If you find it necessary to tweak the directory layout for fonts or the font cache, the key things to know are:

  • the font directory is specified in FOML/fop.xconf and is relative to the FOML directory, which will be the cwd when Fop is executed, and

  • the font cache directory is .fop/fop-fonts.cache, and is relative to the value of Java's user.home which is set explicitly in Foml::XslFoToPdf to the FOML directory.

Usage

<?php
require_once 'FOML/FomlConfig.php';
Foml::RenderInline('templates/report-template.foml', array('var'=$value, ...));
?>

Foml::RenderInline($Template, $ArgsAssocArray)

Expands the FOML document file named by $Template, making the values passed in $ArgsAssocArray available as local variables during the expansion. Finally the resulting PDF document is streamed inline. Generally this will cause the PDF to open in the viewers browser window.

Foml::RenderAttachment($Template,$Filename,$ArgsAssocArray)

Expands the FOML document file named by $Template, making the values passed in $ArgsAssocArray available as local variables during the expansion. Finally the resulting PDF document is streamed as an attachment with the $Filename supplied as the default filename. Generally this will cause browser to prompt the user to save the PDF file.

What's Missing

Although I am already using this library in production, it has some missing features. The most significant weakness is the lack of variable expansion within node parameters. You can current do this:

 %table-column(column-width="30mm")

but not this

 %table-column(column-width="#{$width}mm")

In these cases you can revert to using php to generate the XML like this:

  = "<fo:table-column column-width=\"#{$width}mm\">"
  ...
  = "</fo:table-column>"

This same parser weakness exhibits in another way. For now we are using a simple regex to parse the tag parameters instead of a quote-and-escape-aware parser. The parser searches greedily for the closing ')' which means that while this works okay:

%external-graphic(src="url('https://secure.gravatar.com/avatar/5c914fce9c8e2eaa6dfdde5f22106d74?d=https://a248.e.akamai.net/assets.github.com%2Fimages%2Fgravatars%2Fgravatar-140.png')")/

This doesn't

%fo:block(border-after-style="solid") = join("",array("Thao","Vang","Lor"))

so for now you need to put the inner content on a separate line like this:

%fo:block(border-after-style="solid") 
  = join("",array("Thao","Vang","Lor"))

FOML Syntax

The following syntax is currently supported. Note that HAML-style string expansion #{$likethis} is not yet supported.

XML Elements

XML Element: %

The percent character at the begining of a line, followed immediately by an element name will be rendrered as and XML element. The default namespace "fo" will be used if a namespace is not specified. To use the "xsl" namespace, it should be explicitly specified (eg %xsl:stylesheet).
A trailing '/' at the end of the line, following any arguments, will cause the node to be auto-closed.

Attributes may optionally be specified following the element name. For example

%table-cell
  %flow(flow-name="xsl-region-body")
    %xsl:apply-templates(select="/simpdoca/section[4]")

renders as

<fo:table-cell>
  <fo:flow flow-name="xsl-region-body"> 
    <xsl:apply-templates select="/simpdoca/section[4]"></xsl:apply-templates>
  </fo:flow>
</fo:table-cell>

XML Comments

A line beginning with a single forward-slash renders as an XML comment in the output stream. Any following lines at deeper indent will be included in the comment.

 / Go in peace.
   Oh, I am at peace.

renders as

<!-- Go in peace. Oh, I am at peace. -->

XML Prolog: !!!

Automatically inserts the XML prolog. This should be the first line of any complete FOML document.

!!!

renders as

<?xml version="1.0" encoding="utf-8"?>

Code Evaluation

PHP Evaluation: =

The equals sign followed by a PHP expression renders the evaluation of the expression into the output. A trailing semicolon is NOT required.

%flow
 = $firstname.' '.$lastname

renders as

<fo:flow>
  Walt Kowalski
</fo:flow>

PHP Execution: -

A hyphen flowed by PHP code causes the PHP code to be executed. Any output to stdio will be rendered into the output stream. If the code contains one of if, else, while, for, foreach or elseif, the {} brackets are NOT required.

- $list = array('Walt','Kowalski')
- foreach ($list as $element)
    %table-cell
      %block 
        = $element

renders as

<fo:table-cell>
  <fo:block>
    Walt
  </fo:block>
</fo:table-cell>
<fo:table-cell>
  <fo:block>
    Kowalski
  </fo:block>
</fo:table-cell>

Line Continuation: |

The pipe character as the last character and following whitespace will cause all subsequent lines also ending in a pipe character to be treated as if they were part of the same line. Note that, like HAML, even the final line must end with a pipe character.

%table(                            |
  table-layout="fixed"             |
  width="100%"                     |
  border-collapse="separate"       |
)                                  |

renders as

<fo:table table-layout="fixed" width="100%" border-collapse="separate">
</fo:table>

Code Comments

A line beginning with '-#' is entirely ignored and does not generate any output in the XLS-FO stream.

 -# Comment text

Filters

Filter :include(filename)

The :include filter takes one argument; the name of the file to be included.

 :include('Filename.foml')