A presentation about Twig - the friendly templating engine written in PHP - given in San Francisco for Symfony Live 2011.

1. Symfony Live 2011
being dangerous with Twig
a short story by Ryan Weaver
February 9, 2011

2. being dangerous with Twig
A 5-step guide to using Twig – the fast, secure and
extensible PHP templating engine – to create clean
template code, leverage powerful filters, make your designers
write you love letters, write template functions that don't clog up your
global PHP namespace, take advantage of true template inheritance, hang out with
Django programmers and be able to talk template syntax, enjoy true and non- invasive
output escaping, have more time for your family, control whitespace, add global
variables to all templates, stop lying when you try to tell yourself that <?php echo looks better than a
simple {{, use the fancy for-else control, Rock some macros – little reusable code functions, do awesome stuff like “{% if i is divisibleby 2 %}”,
mediate in the simplicity of your templates and drink more green tea, sandbox your template and whitelist capabilities – allowing Twig to be used in a CMS,
take advantage of the fact that all templates compile to PHP classes that can extend a base class of your choosing, impress your friends by changing the print tag from
{{ var }} to [all-your-base] var [are-belong-to-us], confuse the guy next to you by changing “is” and “is not” to mean the opposite things and convince him that he's misunderstood
how logical expressions are used in programming languages all along, create a custom tag that takes the body of its block and tweets it,
write templates the expresses presentation and not program logic.
Ryan Weaver
Symfony Live 2011

3. @weaverryan
» symfony
» documentation
» collaboration
» the lovely @leannapelham

4. iostudio: flying the symfony flag
●
Advertising & Integrated Marketing Solutions
• coming to you from
» Nashville, TN
» Washington, D.C.
• 150 employees
• and we're hiring!

5. act 1
Why Twig?

6. because template
engines are awesome

8. Template engines
A template engine allows you to render a
presentation (HTML, XML, etc) via a template
in a controlled environment
It should allow special functionality that
makes creating templates easier (helpers,
template inheritance, etc)

9. a template engine
is a tool

10. why not just render
PHP templates?

11. PHP templating woes
» rendering template files is a hack: an include
statement with output-buffering control
» no or faked template inheritance
» no isolation: PHP templates suck in any global
variables or functions available

12. we need the brevity
of templates
with the isolation of
object-oriented
programming

13. so give me some Twiggy pudding
Twig is: Twig offers:
» fast » true inheritance
» flexible » real output escaping
» concise » tons of filters
» secure » custom tags
» fully-featured » great documentation
» Extensible » global variables
» designer-friendly » the “for-else” control
http://www.twig-project.org

14. Twig is concise
and each template
compiles to an actual
PHP object

15. seeing is believing

19. a moment of
templating zen

20. “The template system is meant to
express presentation, not program
logic.”
- Django documentation

21. Twig can easily be
used anywhere

23. act 2
Twig's simple life

24. Twig's three tags
Twig parses just three simple tags:
» comment tag
» print tag
» block tag

25. a. do nothing (comment tags)
{# comment #}
» totally ignored when rendered

26. b. say something (print tags)
{{ 'print me!' }}
» prints the given expression
» think “<?php echo”
» If you're ultimately printing something, use
this tag

27. c. do something (block tags)
{% set foo = 'inside a block tag' %}
» used mostly for control-flow statements like if, for,
include and block
» can have beginning and end tags
» if you're *doing* something and not *printing*
something, use this tag

28. Twig's three tags
» do nothing: {# comment tag #}
» say something: {{ print tag }}
» do something: {% block tag %}
it's just that simple

29. act 3
Everything is an
expression

30. expressions: Twig guts
» like PHP, most everything inside a tag
is an expression
» expressions are the most interesting and
flexible part of Twig

31. Expressions Block names
Block-specific tokens

32. an expression can
consist of many
different things

33. strings, variables, arrays,
functions, filters, tests,
subscripts...

34. strings, numbers and variables
» like any language, strings, numbers and
variables are commonplace

35. arrays and hashes
» arrays use [], hashes use {}

36. operators
» twig has operators just like PHP, but extensible
and with some extras

37. filters
» a filter always follows a pipe (|) and modifies the
value that precedes it
» a filter may or may not take arguments

38. functions
» just like PHP, returns a value based on some input

39. twig expresses himself
» strings, numbers and variables
» arrays and hashes
» operators
» filters
» functions
hey – it's simple like PHP, but flexible...

40. act 4
twig on the battlefield

41. the test...
» a template that displays a list of “widgets” in
odd-even rows
» render tags and other info about each widget
» create basic, clean pagination

42. block tag
print tag

43. Let's clean things up

44. filter to title-case
the widget name
filters to strip tags
and shorten the
widget's description

45. your presenter is lying to you...
» the “truncate” filter isn't part of Twig, but
is available via a repository of extensions
» Everything in Twig is loaded via an Extension
(even the core stuff)
» Extensions are easy to use and create – we'll
prove it later
* https://github.com/fabpot/Twig-extensions

46. odd/even classes
like a boss

47. Twig function cycles through
the given array items
Special variable available inside
all “for” loops.
The “loop” variable knows other
tricks like “loop.last” and
“loop.revindex”

48. flex some filters

49. apply the date filter
chain filters to turn a list of tags
into a comma-separated list

50. convenience,
readability

51. even management
knows what this does

52. pagination?

53. function returns a positive
radius of numbers around the
center (e.g. 3, 4, 5, 6, 7)
the awesome loop variable tells us
when we're in the last iteration

54. the audacity: your speaker just lied again
» but.... the “radius” function doesn't actually
exist in Twig.
but since it's pretty handy, let's create it!

55. act 5
Twig extensions

56. Twig extensions
everything in Twig is loaded by an “Extension” class:
» filters
» functions
» operators
» tests (e.g. divisbleby)
» custom tags
Extensions are EASY!

57. step 1: create a class that extends Twig_Extension

58. step 2: tell Twig about the extension

59. step 2: tell Twig about the extension (Symfony2)
* don't forget to import this file from your
application's configuration (i.e. app/config/config.yml)

60. step 3: add some guts to the extension class

61. step 4: Celebrate!!!
* buy a round of drinks
* watch the sun set
* kiss that cute girl at the
coffee shop

62. I want more!
ok great – do some reading!
» http://www.twig-project.org/doc/advanced.html
» http://www.twig-project.org/doc/extensions.html
seriously – the Twig docs are quite excellent

63. act 6
after-dinner mint
mmm

64. screw with the Twig syntax
» because Twig is totally sandboxed (i.e. you
control exactly what can and cannot be done
inside a template, Twig is a perfect fit for a CMS.
» and if Twig's syntax scares your clients... change it!

66. cool, what about
debugging?
a debug tag ships with
the twig-extensions

67. the “debug” extension is available for you
in Symfony2 - just enable it

68. prints every variable
available
prints the foo variable

69. but we've only just
scratched the surface

70. there's much much more
» inheritance name can be:
* an item on an array
* property on an object
» macros (reusable code bits) * getName()
» subscripts
or you can force it to
*just* fetch “name”
as an array item

71. Twig, he's a people-person
» Twig's loves contributions, so *get involved*!
» https://github.com/fabpot/twig
» https://github.com/fabpot/twig-extensions
» http://groups.google.com/group/twig-users

72. thank you
Ryan Weaver
iostudio
@weaverryan
www.thatsquality.com
ryan [at] thatsquality.com
reach out to me – i'd love to hear from you!
comments, feedback, questions
http://joind.in/talk/view/2601