Grav - Twig Filters & Functions

In this chapter let's study about Twig Filters and Functions. Filters are used to format the data the way you want and output. Functions are used to generate contents.
Twig templates are text files that contain expressions and variables replaced by values. Twig uses three types of tags.

• Output tags: It is used to display evaluated expressions result. It uses below syntax.
  

  {{  Place Your Output Here  }}
  	

• Action Tags: It is used to execute statements. It uses below syntax.
  

  {%  executable statements are placed here  %}
  	

• Comment tags: It is used to write comments in Twig template file. It uses below syntax.
  

  {#  write your comment here  #}
  	

Twig Filters

Twig Filters uses the | character to apply filters to Twig variable followed by the filter name. Arguments can be passed in paranthesis similarly like Twig functions.
Following table shows Twig Filters used in Grav:

Filters	Description	Example
Absolute URL	It takes the relative path and convert it to an absolute URL.	'<img src="/some/path/img.jpg"/>' | absolute_url converts to: <img src = "http://learn.getgrav.org/some/path/img.jpg" />
Camelize	It converts a string to CamelCase format.	'contact_us'| camelize converts to: ContactUs
Contains	It looks for a string in another string and displays 1 if it finds the string.	'This is some string' | contains('some') it outputs: 1
Defined	You can check if some variable is defined or not. If variable is not defined you can provide a default value.	set header_image_width = page.header.header_image_width|defined(900) It sets header_image_width with value 900 if it’s not defined.
Ends-With	You can determine whether a string ends with a given string by using Ends-With filter.	'this is an example for ends-with filter' | ends_with('filter') it displays as: True
FieldName	It filters the field name by changing dot into array notation.	'field.name'|fieldName displays it as: field[name]
Humanize	It is used to convert a string to human readable format.	'some_text_to_read'|humanize it displays as: Some text to read
Ksort	It sorts an array map using key.	{% set ritems = {'orange':1, 'apple':2, 'peach':3}|ksort %} {% for key, value in ritems %}{{ key }}:{{ value }}, {% endfor %} it displays as: apple:2, orange:1, peach:3,
Left Trim	It is used to remove white spaces at beginning of a string and removes the matching character given from left side of the string.	'/strip/leading/slash/'|ltrim('/') is displayed as: strip/leading/slash/
Markdown	It is used to convert the string containing markdown into HTML using the markdown parser of Grav.	'## some text with markdown'|markdown is displayed as: some text with markdown
MD5	The md5 hash for the string can be created by using this filter.	'something'|md5 is displayed as: 437b930db84b8079c2dd804a71936b5f
Monthize	By using Monthize filter we can convert an integer number of days to number of months.	'61'|monthize it displays as: 2
Nice Time	By using Nice Time filter we can output a date in nice human readable time format.	page.date|nicetime(false) is displayed as: 3 hrs ago
Ordinalize	Ordinals ( like 1st,2nd, 3rd ) can be given to integers by using Ordinalize filter.	'78'| ordinalize is displayed as: 78th
Pluralize	A string can be converted to its plural English form by using Pluralize filter.	'child'|pluralize is displayed as: children
Randomize	This is filter randomize the provided list. If parameter contains any values then those values are skipped from randomizing.	{% set ritems = ['one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten']|randomize(3) %} {% for ritem in ritems %}{{ ritem }}, {% endfor %} Is displayed as: one, two, three, eight, six, five, nine, seven, ten, four,
Right Trim	It is quite similar to left trim except it removes whitespaces and matched character from right side of the string.	'/strip/leading/slash/'|rtrim('/') is displayed as: /strip/leading/slash
Singularize	A string can be converted to English singular version by using Singular filter.	'vehicles'|singularize is displayed as: vehicle
Safe Email	Safe Email filter is used to convert an email address into ASCII characters so that it makes harder for email spam.	"someoneemailaddress@domain.com"|safe_email it outputs: someoneemailaddress@domain.com
SortByKey	It is used to sort the array map using keys.	{% set people = [{'email':'john@gmail.com', 'id':3}, {'email':'melw@fdd.com', 'id':1}, {'email':'nancy@fb.com', 'id':7}]|sort_by_key('id') %} {% for person in people %}{{ person.email }}:{{ person.id }}, {% endfor %} it displays: melw@fdd.com:1, john@gmail.com:3, nancy@fb.com:7,
Starts-With	You can determine whether a string starts with a given string by using Starts-With filter.	'this is an example for starts-with filter' |starts_with('this') It outputs: true
Translate	It is used to translate a string into current language. You can refer multi-language documentation for more detailed information.	MY_LANGUAGE_KEY_STRING it displays: 'Some text in English'
Translate Admin	It translates a string into current language which is set in the user.yaml file.
Titleize	A string is converted into Title Case format by using Titleize.	'welcome page'|titleize is displayed as: Welcome Page
UnderScoreize	A given string is converted to under_scored format by using UnderScoreize filter.	'ContactUs'|underscorize is converted to: contact_us
Truncate a string	You can use Truncate to truncate a string or shorten the string, you must specify number of characters.	'one sentence. two sentences'|truncate(5) truncates to: one s... You can use true as parameter if you don't want to truncate the string to closest sentence-end after the given number of characters. 'one sentence. two sentences'|truncate(5, true) truncates to: one sentence You can also strip HTML text, but you should use striptags filter before truncate filter. '<p>one <strong>sentence<strong>. two sentences</p>'|striptags|truncate(5) is displayed as: one s

Twig Functions

Twig Functions are directly called by passing the parameter. Following table lists the functions:

Functions	Description	Example
Array	This function cast a value to array.	array(value)
Authorize	This function makes an authenticated user is authorized to see a resource and accepts permission string or array of permission strings.	authorize(['admin.statistics', 'admin.super'])
Dump	It accepts a valid twig variable and dumps it into the Grav debugger panel. However the debugger should be enabled to see messages tab values.	dump(page.header)
Debug	This works same as the dump() function.
Gist	This function creates Gist embed code based on Github Gist ID.
Random String Generation	This function will create a random string with specified number of characters. These strings can be used as unique id or key.	generate_random_string(10)
Repeat	This function will repeat the string for given amount of time.	repeat('Grav ', 10) will repeat Grav 10 times.
String	Generates a random string of specified character length.	ta (23)
Translate Array	It is a functions connected with |ta filter.
Url	This filter will create a URL and it will also convert PHP URL streams into valid HTML resources. If the URL cannot be resolved a default value can be passed.	url('theme://images/logo.png') | default('http://www.placehold.it/150x100/f4f4f4')
Translate	Using Translate filter, a string is translated as the |t filter.	t('SITE_NAME') is translated to: Site Name