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Help Contents → Parser function

A "parser function" is a template-like construct which returns a value based on at least one unnamed parameter, separated from the function name by a colon ":"; there may be more parameters which, like those of ordinary templates, are each preceded by "|". The syntax can be written with or without a leading hash character (#):

{{functionname: argument 1 | argument 2 | argument 3...}}

for:

or

{{#functionname: argument 1 | argument 2 | argument 3...}}


The distinction with variables is that the latter do not have any arguments, and also no colon.

For each language there is a file like MessagesEn.php specifying for each variable and parser function whether the name is case-sensitive.

Usually variables are case-sensitive and parser functions are not. To some variables ":R" can be added ("raw" modifier), but, although now a parser function, the name is still case-insensitive. Also the names DISPLAYTITLE and DEFAULTSORT are case-sensitive.

MediaWiki's core parser functions are listed below and in Magic words.

Formatting

LC

Makes a text lowercase and removes newlines and spaces from the start and end.

{{lc: AbC dEf }} yields abc def.
{{lc: Ä Β Ç }} yields ä β ç.

UC

Makes a text uppercase and removes newlines and spaces from the start and end.

{{uc: AbCdEf }} yields ABCDEF.
{{uc:ä β ß}} yields Ä Β SS, expected: Ä Β SS. Don't expect too much.

LCFIRST

Makes the first character lowercase and removes newlines and spaces from the start and end: {{lcfirst: Ab Cd }} yields ab Cd.

UCFIRST

Makes the first character uppercase and removes newlines and spaces from the start and end: {{ucfirst: aB cD }} yields AB cD.

URLENCODE

Removes newlines and spaces from the start and end, and converts the remaining text into URL-friendly format by replacing spaces with "+" and other URL formatting characters with their escaped equivalents: {{urlencode:hello world ?&=#/:}} yields hello+world+%3F%26%3D%23%2F%3A.

ANCHORENCODE

For anchors within a page use {{anchorencode}} instead of {{urlencode}}. The results of a call to {{anchorencode}} are compatible with intra-page references generated for [[#link]]s, while {{urlencode}}-generated values are not necessarily so.

NS

Gives the namespace name for a given namespace number or name:

Code
with Number		 Code
with Name		 Returns
with Number		 Returns
with Name
{{ns:-2}} {{ns:media}} Media Media
{{ns:-1}} {{ns:special}} Special Special
{{ns:0}} (not applicable) (not applicable)
{{ns:1}} {{ns:talk}} Talk Talk
{{ns:2}} {{ns:user}} User User
{{ns:3}} {{ns:user_talk}} User talk User talk
{{ns:4}} {{ns:project}} Memory Alpha Memory Alpha
{{ns:5}} {{ns:project_talk}} Memory Alpha talk Memory Alpha talk
{{ns:6}} {{ns:image}} File File
{{ns:7}} {{ns:image_talk}} File talk File talk
{{ns:8}} {{ns:mediawiki}} MediaWiki MediaWiki
{{ns:9}} {{ns:mediawiki_talk}} MediaWiki talk MediaWiki talk
{{ns:10}} {{ns:template}} Template Template
{{ns:11}} {{ns:template_talk}} Template talk Template talk
{{ns:12}} {{ns:help}} Help Help
{{ns:13}} {{ns:help_talk}} Help talk Help talk
{{ns:14}} {{ns:category}} Category Category
{{ns:15}} {{ns:category_talk}} Category talk Category talk
{{ns:102}} {{ns:portal}} Portal Portal
{{ns:103}} {{ns:portal_talk}} Portal talk Portal talk
{{ns:110}} {{ns:forum}} Forum Forum
{{ns:111}} {{ns:forum_talk}} Forum talk Forum talk
{{ns:112}} {{ns:ma_help}} MA Help MA Help
{{ns:113}} {{ns:ma_help_talk}} MA Help talk MA Help talk
{{ns:828}} {{ns:module}} Module Module
{{ns:829}} {{ns:module_talk}} Module talk Module talk

Also, for example, {{ns:{{ns:12}} talk}} yields Help talk.

NS:1

{{ns:{{ns:0}} talk}} works as well: Talk, as do the following constructs:

{{ns:01}} yields Talk, {{ns:+1}} yields Talk, {{ns:TALK}} yields Talk, and {{ns:{{ns:1}}}} also yields Talk. Note that the function is not case sensitive.

NS:0

#{{ns:0}}# yields ##, an empty string. This is often handy, less vulnerable than a template void or similar, and less cryptic than magic words like __END__.

In constructs like {{ {{#if: {{{T|}}} | {{{T}}} | ns:0}} }}, where the parameter T is normally the name of a template to be evaluated and can be undefined or empty, {{ns:0}} is then a clean empty string. Without it {{}} would result in {{}}.

Please note that {{ns:{{ns:0}}}} fails: . NS cannot handle an empty {{ns:0}} argument.

An empty section title like above is obtained using, in this case, ==== {{ns:0}} ====. This is dubious, but arguably better than using the same trick to get invisble section headers twice on a page. At least /* {{ns:0}} */ makes sense in the edit history, if there's only one section using this particular trick.

As shown in the table of contents this and similar tricks result in non-functional links. In conjunction with __NOTOC__ it's less harmful, and maybe useful to get edit links for invisible sections with categories and interlanguage links. Other possibilities for different invisible section headers:

  1. === __NOTOC__ ===
  2. === ===
  3. ===   ===
  4. ===   ===

URLs, etc.

{{localurl:fullpagename}} /wiki/Fullpagename
{{localurl:page|query=x}} /wiki/Page?query=x
{{localurl:a&b! c}}
{{localurle:a&b! c}} 		/wiki/A%26b!_c
/wiki/A%26b!_c
{{urlencode:a&b! c}} a%26b%21+c
{{fullurl:fullpagename}} https://memory-alpha.fandom.com/wiki/Fullpagename
{{fullurl:ab}} https://memory-alpha.fandom.com/wiki/Ab
{{fullurl:a b}} https://memory-alpha.fandom.com/wiki/A_b
{{fullurl:ab|u=v}} https://memory-alpha.fandom.com/wiki/Ab?u=v
{{fullurl:m:a b|u=v}} https://meta.wikimedia.org/wiki/a_b?u=v
{{fullurl:m:ab|u=v}} https://meta.wikimedia.org/wiki/ab?u=v
{{fullurl:a b|u=v}} https://memory-alpha.fandom.com/wiki/A_b?u=v
{{fullurl:a b|u=v w}} https://memory-alpha.fandom.com/wiki/A_b?u=v w
{{fullurl:a&b!|u=v}}   https://memory-alpha.fandom.com/wiki/A%26b!?u=v
{{fullurle:a&b!|u=v}}  https://memory-alpha.fandom.com/wiki/A%26b!?u=v

Note that with the interwiki prefix the format "wiki/" is used even for edit pages etc., while it does not write the page name in canonical form.

For interwiki links localurl and fullurl give the same:

{{localurl:wikipedia:a}} http://en.wikipedia.org/wiki/a
{{fullurl:wikipedia:a}} https://en.wikipedia.org/wiki/a

The parser function localurl: replaces spaces by underscores and special characters by escape codes, e.g. {{localurl:a !}} yields /wiki/A_!. The main purpose was to create a link to a given page in external link style in the same project or a project which uses the same string in the URL between the server name and the page name. This function is now better served by less verbose fullurl: constructs, {{fullurl:page}} is a shorthand for {{SERVER}}{{localurl:page}}.

Both fullurle: and localurle: performed additional character escaping on the resulting link, but no example is known where that still has any additional effect.

Note that fullurl: and localurl: don't encode special characters and spaces in the optional query-string parameter. At least for spaces this will result in broken URLs:
{{fullurl:m:Special:Contributions|target=Jimbo Wales&limit=10}}
https://meta.wikimedia.org/wiki/Special:Contributions?target=Jimbo Wales&limit=10

With target={{urlencode:Jimbo Wales}}&limit=10 as query-string it works:
https://meta.wikimedia.org/wiki/Special:Contributions?target=Jimbo+Wales&limit=10

The new urlencode: encodes spaces as "+", not "_" or the generally supported "%20"; this might have interesting effects, so take care. Leading and trailing spaces are stripped, but all internal spaces are preserved: {{urlencode:  @  !  }} yields %40++%21.

For obvious reasons encoding "}}" or "|" cannot work directly. Don't encode "=", "&", or ";" in structured query-strings unless you really want it.

Example

Say you want to create a link in a template to the block log for blocked usernames: "{{fullurl:Special:Log/block|user=User:{{{1}}} }}". This won't work with spaces in the name like "Example blocked user" (unless they are manually underlined) as you'd get: "https://memory-alpha.fandom.com/wiki/Special:Log/block?user=User:Example blocked user", so what you can do is escape it with "{{fullurl:Special:Log/block|user=User:{{urlencode:{{{1}}}}} }}", giving you "https://memory-alpha.fandom.com/wiki/Special:Log/block?user=User:Example+blocked+user".

Also, the magic words for page name like {{PAGENAME}}, {{FULLPAGENAME}}, etc. all have "escaped" versions: {{PAGENAMEE}}, {{FULLPAGENAMEE}}, etc.

#language:

{{#language: code}} gives the local language name of selected RFC 3066 language codes, otherwise it returns the input value as is. For a complete list see the IANA registry.

{{#language:da}} yields dansk
{{#language:fo}} yields føroyskt
{{#language:zh}} yields 中文
{{#language:zh-min-nan}} yields 閩南語 / Bân-lâm-gú
{{#language:ang}} yields Ænglisc
{{#language:tlh}} yields tlh (Klingonese)
{{#language:frr}} yields Nordfriisk (missing, introduced 2006)
{{#language:mw}} yields mw (no language code as of 2006)

Use of result

The result, like that of a variable or template, and like a template parameter value, can be used in the following ways: 

* the name of a template: {{tl|{{lc:EXAMPLE}}}}
* the name of a variable: {{ {{uc:pagename}}}}
* the name of a parser function: {{ {{uc:lc}}:EXAMPLE}}
* the name of a template parameter: {{tl|{{#expr:3-2}}=Example}}
* the value of a template parameter: {{tl|Example|{{#expr:3-2}}}}
* a template parameter default value: {{{1|{{#expr:7-2}}}}}
* the name of a switch parameter: {{#switch:2|{{#expr:3-1}}=A}}
* the value of a parser function parameter: {{#ifeq:{{lc:ExAmPlE}}|example|yes}}
* the target or label of an internal link: [[Template:{{lc:EXAMPLE}}|{{uc:example}}]]
* the target or label of an external link: [http://memory-alpha.org/wiki/Template:{{lc:EXAMPLE}} {{uc:example}}]

gives:

The result cannot be used inside XML-style extension tags:

<math>{{#expr:3-1}} \over 3</math> gives Failed to parse (syntax error): {\displaystyle {{#expr:3-1}} \over 3 }

The workaround is to use the parser-function equivalents for such tags:

{{#tag:math|{{#expr:3-1}} \over 3}} gives

Expansion

The first step in expanding any wikitext is identifying the templates, parser functions, variables and parameters from the braces, pipes and semicolons. For a parser function the next step is expanding the wikitext for the name of the parser function.

Suppose for example that it is #ifexpr. Then the next step is expanding the condition. Based on that either the wikitext for the then-part or that for the else-part is expanded.

This is illustrated with {{#ifexpr:1|{{tl|example}}|{{bad example}}}} {{#ifexpr:0|{{bad example}}|{{tl|example}}}} giving {{example}} {{example}}. A page with this wikitext transcludes example only (with the old preprocessor also bad example).

Interpretation of a parser function as a template

In some cases a "wrong" parser function call is interpreted as a template call, which results in an entry in the templatelinks table, which in turn results in an entry in the list of pages included in a page (on the edit box of the source page) and what links here of the target page.

This applies, for example, for localurl: and fullurl: if the parameter is not a valid page name, while "Template:localurl:" and "Template:fullurl:" followed by the parameter is. This is the case if the parameter is a namespace prefix followed by a colon, such as:

This entry in the templatelinks table occurs even if the result produced is not rendered due to a conditional parser function. This may occur in practice using, for example:

Thus, the list of templates transcluded in a page may be polluted with the entries of the non-existing template Template:Fullurl:Template: and similarly for other namespace names instead of the second "Template", and for "localurl" instead of "fullurl". One remedy is:

Substitution

Applying "subst:" to a parser function works:

{{subst:LC:AbC}} yields abc.

Note that unless a technique like optional recursive substitution is used, substituting a template which uses a parser function does not replace that parser function with its result.

See also Help:Substitution at MediaWiki.org.

See also