M:Help:ParserFunctions

Other languages: Template:ParserFunctions Template:H:h Template:MoveToMediaWiki Template:Shortcut Template:Otheruses4

The MediaWiki extension ParserFunctions is a collection of parser functions (note the difference between the name of the collection, and the general term). These parser functions have a hash character in front of the function name, so they typically have the syntax:

Template:Ft

Please note that ParserFunctions are unavailable in some MediaWiki installations, check out Special:Version below Parser hooks, individual functions such as expr and switch are listed below Parser function hooks.

Functions

The extension defines ten functions: expr, if, ifeq, ifexist, ifexpr, iferror, switch, time, rel2abs, and titleparts.

#expr:

• syntax: Template:Ft

The expr function computes mathematical expressions based on permutations of numbers (or variables/parameters that translate to numbers) and operators. It does not recognize strings (use ifeq below instead). The accuracy and format of numeric results varies with the server's operating system.

The main operators are listed below. For more, see Help:Calculation

In a complex expression, operators are evaluated from left to right with the following precedence (explained in more detail in Help:Calculation):

1. grouping (parentheses);
2. unary (+/- signs and NOT);
3. multiplicative (*, /, div, mod);
4. additive (+ and -);
5. round;
6. comparative (=, !=, <, >, etc.);
7. logical AND;
8. logical OR.

When evaluating as boolean, "0" is considered false and any other non-space value is true (boolean true is represented as "1").

Decimal numbers use "." as a decimal point (formatnum: can be used to change the decimal point to a comma for the appropriate locales). Scientific notation with E plus exponent is meanwhile supported also on input for expressions (see Help:Calculation).

Operator	Operation	Example	Result
none		Template:Ft	1.2345678901234E+14
		Template:Ft	1.0E-6
Arithmetic
+	Unary positive sign	Template:Ft	210
-	Unary negative sign	Template:Ft	210
*	Multiplication	Template:Ft	210
/ div	Division	Template:Ft Template:Ft	4.2857142857143 4.2857142857143
+	Addition	Template:Ft	37
-	Subtraction	Template:Ft	23
Logic
not	Unary NOT logical NOT	Template:Ft Template:Ft	7 7
and	Logical AND		0
or	Logical OR		1
Comparison
=	Equality (numerical & logical)	Template:Ft	0
<> !=	Inequality, logical exclusive or	Template:Ft Template:Ft	1 1
<	Less than		0
>	Greater than		1
<=	Less than or equal to		0
>=	Greater than or equal to		1
Other
( )	Grouping operators	Template:Ft	259
mod	"Modulo" truncates the numbers to whole numbers, divides the left number by the right, and returns the remainder that could not be divided. Note: div and mod are different from all programming languages.	Template:Ft Template:Ft Template:Ft	2 -2 0
round	Rounds off the number on the left to the power of 1/10 given on the right.	Template:Ft Template:Ft Template:Ft Template:Ft	4.2857 4.3 1900 -3
trunc	Removes all decimals.	Template:Ft Template:Ft	1 -1
floor	Rounds off a decimal number to the closest integer that is less than or equal to the given number.	Template:Ft Template:Ft	1 -2
ceil	Rounds off a decimal number to the closest integer that is more than or equal to the given number.	Template:Ft Template:Ft	2 -1

#if:

• syntax:

  Template:Ft

  Template:Ft

The if function is an if-then-else construct. The condition is always true unless it is empty or whitespace-only. The code in the second argument is parsed if the condition is true, and the third argument is parsed if the condition is false (either or both may be blank, and the code-if-false argument can be omitted entirely).

The condition is evaluated as text, so mathematical expressions will always evaluate as true; to use expressions as conditions, see #ifexpr. It is not possible to distinguish between an undefined parameter in a template and a blank one (it is possible with #ifexpr).

Examples:

• Template:Ft = do if true
• Template:Ft = do if true
• Template:Ft = do if false

#ifeq:

• syntax:

  Template:Ft

  Template:Ft

The ifeq function compares two strings or numbers, and returns the second argument if they are equal and the third argument if not equal (either or both may be blank, and the code-if-not-equal argument can be omitted entirely; there is thus no ifneq function, since you can just use ifeq and leave <code if equal> blank).

Comparison of strings is case-sensitive (for example, A != a). If both strings can be interpreted numerically, they will be compared numerically (for example, 01 = 1); To force a string-based comparison, add non-numerical characters (such as quotes ") to both compared arguments.

It is possible to distinguish between undefined and empty template parameters by comparing default values (if the parameter is defined, it will overwrite the default value even if blank):

• Template:Ft = parameter not defined

Issues:

• Text between <nowiki> tags is temporarily replaced by a unique code. This affects comparisons: Template:Ft returns "not equal".

#ifexist:

Template:Ft returns one of two results based on whether or not a particular page exists.

Template:Ft

The usual case-sensitivity applies: if a page exists then also a non-canonical name for that page gives a positive result. E.g. on Meta:

Template:Ft gives RFC 3092, because Bugs exists

Template:Ft gives RFC 3092, because bugs is in canonical form the existing Bugs

Template:Ft gives RFC 3092 because BUGS does not exist

Template:Ft gives Oops although m:Help:Calculation exists, because of the interwiki prefix.

The first parameter is the title to check for, the second is the positive result, and the third, the negative result. If the parameter passed does not produce a valid title object, then the result is negative.

m:Template:exists (backlinks, edit) gives the same result, except that the result is positive for an interwiki link. You can also handle an interwiki link differently with m:Template:if interwiki link (backlinks, edit).

Template:Ft doesn't handle relative paths (like '../foo'), for that, use it in combination of Template:Ft.

The page where {{#ifexist:foo}} appears is listed on Special:Whatlinkshere/foo (as a page which links to foo), see below.

On Wikimedia wikis there is a maximum for the number of distinct pages for which #ifexist is called on a page. A call of #ifexist after a transclusion of the same page does not require an extra database query and is therefore not counted. A call beyond the maximum returns "false". The html-source of each page shows the counted number of calls, as well as the maximum. The maximum is currently 500, and it has been announced that this will be lowered to 100. [1].

Template:Ft can correctly check Special pages as well:

Template:Ft gives works

Template:Ft gives doesn't work

#ifexpr:

Template:Ft evaluates a mathematical expression (see #expr) and returns one of two strings depending on the result.

Template:Ft

If the expression evaluates to zero, then the else text is returned, otherwise the then text is returned. Expression syntax is the same as for expr.

Example:

Template:Ft yes -- Because 10 is greater than 9.

At the moment the else text is also returned for an empty expression:

Template:Ft gives or else

Omitting both then text and else text gives no output except possibly an error message; this can be used to check the correctness of an expression, or to check the wording of the error message (emulated assertions, forced errors):

Template:Ft -- no result, hence "1/{{#ifeq: {{ns:4}}|Meta|1|0}}" is a correct expression

Template:Ft

Template:Ft correct -- "1=2" is a correct Boolean expression (not to be confused with one with the value 1, representing "true")

Template:Ft correct -- "1E2" is now also allowed in expressions

Template:Ft wrong -- "1/0" not allowed

Template:Ft wrong ("a=b" not allowed, to compare strings use #ifeq)

Example of an application: {{ #if: {{#ifexpr: {{PAGENAME}} }} || action if PAGENAME is a number (or correct numeric expression) }}

For another application, see also m:Template:evalns (backlinks, edit).

#switch:

switch compares a single value against multiple others, returning a string if a match is found. The syntax is basically:

Template:Ft begin <comparison value>
 | <value1> = <result1>
 | <value2> = <result2>
 | ...
 | <valuen> = <resultn>
 | <default result>
Template:Ft end

switch will search through each value passed until a match is found with the comparison value. When found, the result for that value is returned (the text string after the equal sign). If no match is found, but the last item has no equal sign in it, it will be returned as the default result. If your default result must have an equal sign, you may use #default:

Template:Ft begin <comparison value>
 | <value> = <result>
 | #default = <default result>
Template:Ft end

Note that it's also possible to have "fall through" for values (reducing the need to duplicate results). For example:

Template:Ft begin <comparison value>
| <value1>
| <value2>
| <value3> = <result1, 2, 3>
| ...
| <valuen> = <resultn>
| <default result>
Template:Ft end

Note how value₁ and value₂ contain no equal sign. If they're matched, they are given the result for value₃ (that is, whatever is in result₃).

As for #ifeq: the comparison is numerical where possible:

Template:Ft gives Yes

Template:Ft gives No

The matched value can be empty, therefore the following constructs are equivalent:

Template:Ft gives empty

Template:Ft gives empty

Comparison of strings is case-sensitive:

Template:Ft gives UPPER

Template:Ft gives UPPER

Template:Ft gives lower

This is not to be confused with the fact that parser function names are case-insensitive:

Template:Ft gives UPPER

To have the #switch statement be case-insensitive, use the construct {{lc:}} or {{uc:}}

Template:Ft gives lower

Template:Ft gives lower

Template:Ft gives lower

This is usually used in templates, when you want to have case-insensitivity on in param values:

Template:Ft begin Template:Ft sub
| a
| b
| c = '''''abc''' or '''ABC'''''
| A
| B
| C = ''Memory corruption due to cosmic rays''
| #default = N/A
Template:Ft end

gives abc or ABC

#switch may be used instead of #ifeq:

Template:Ft gives true

Template:Ft gives true

#time:

Template:Ft is a time and date formatting function. The syntax is:

Template:Ft
Template:Ft

If the time is not specified, the time at which the article is converted to HTML is used. Note that due to caching, this may be up to a week different to the time at which the article is viewed. Manual updates may be required, this can be achieved by saving the page without making any changes (a "null edit") or viewed with action=purge in search string of URL or viewed by a user whose option is "Disable page caching".

The format parameter is a format string similar to the one used by PHP's date.

The following format codes have the same meaning as in PHP. Significant differences from PHP's behaviour, apart from internationalisation (i.e. language and locale differences), should be considered an error of ParserFunctions and should be reported. All numeric format codes return numbers formatted according to the local language, use the xn code described below to override this.

Code	Description	Example output	Current output
Year:
Y	The 4-digit year.	e.g. 2006	2024
y	The 2-digit year.	00 to 99, e.g. 06 for year 2006.	24
Month:
n	The month number, not zero-padded.	1 to 12	11
m	The month number, zero-padded.	01 to 12	11
M	An abbreviation of the month name. Often internationalised.	Jan to Dec	Nov
F	The full month name. Often internationalised.	January	November
Week:
W	ISO 8601 week number (ISO years have full weeks from monday to sunday, and ISO week number 1 always contains January 4 or the first thursday of the civil year), zero-padded.	01 to 52 or 53 (depends on year)	46
Day:
j	The day of the month, not zero-padded.	1 to 31	13
d	The day of the month, zero-padded.	01 to 31	13
z	The day of the year (starting from 0)	0 to 364, or 365 on a leap year	317
D	An abbreviation for the day of the week. Rarely internationalised.	Mon to Sun	Wed
l	The full weekday name. Rarely internationalised.	Monday to Sunday	Wednesday
N	ISO 8601 day of the week (according to the ISO 8601 week).	1 (for Monday) through 7 (for Sunday)	3
w	number of the day of the week (according to the American week).	0 (for Sunday) through 6 (for Saturday)	3
Hour:
a	am (between 01:00:00 and 12:59:59 on the same day) or pm, with lowercase (used with the 12-hour format).	am or pm	am
A	Same as with code a above, but with uppercase.	AM or PM	AM
g	12-hour format of the hour without leading zeros (one or two digits, used with am/pm or AM/PM).	1 to 12	9
h	12-hour format of the hour, with leading padding zero (two digits, used with am/pm or AM/PM).	01 to 12	09
G	24-hour format of the hour, without leading padding zero (one or two digits).	0 to 23	9
H	24-hour format of the hour, with leading padding zero (two digits).	00 to 23	09
Minutes and seconds:
i	The minute, with leading padding zero (two digits).	00 to 59	06
s	The second, with leading padding zero (two digits).	00 to 59	58
U	Seconds since January 1 1970 00:00:00 GMT.	0 to infinite	1731488818
Miscellaneous:
L	Whether it's a leap year.	1 if it is a leap year, 0 otherwise.	1
t	Number of days in the month.	28 to 31	30
c	ISO 8601 formatted date, same as {{#time:Y-m-dTH:i:s+00:00}}.	fixed length string	2024-11-13T09:06:58+00:00
r	RFC 2822 formatted date, same as {{#time:D, j M Y H:i:s +0000}} with weekday name and month name not internationalised.	variable length string	Wed, 13 Nov 2024 09:06:58 +0000

The following format codes are extensions to the PHP syntax:

Code	Description
xn	Format the next numeric code as a raw ASCII number. For example, in the Hindi language, Template:Ft produces ०६, 06.
xN	Toggle a permanent raw number formatting flag. Like xn, except it lasts until the end of the string or until the same code appears again.
xr	Format the next numeric code as a roman numeral. Only works for numbers up to 3000.
xg	Output the genitive form of the month name, for languages which make such a distinction between genitive and nominative.
xx	A literal "x"
xij	The day of the month in Iranian calendar.
xiF	The full month name in Iranian calendar
xin	The month number in Iranian calendar
xiY	The full year in Iranian calendar
xjj	The day of the month in Hebrew calendar
xjF	The full month name in Hebrew calendar
xjx	Genitive form of the month name in Hebrew calendar
xjn	The month number in Hebrew calendar
xjY	The full year in Hebrew calendar
xkY	The full year in Thai solar calendar

Any unrecognised character will be passed through to the output unmodified. There are also two quoting conventions which can be used to output literal characters.

• Characters enclosed in double quotes will be considered literal (with the quotes themselves removed). Unmatched quotes will be considered literal quotes. Example:
  • Template:Ft → The month is November
  • Template:Ft → 06'58"
• Backslash escaping as in PHP's date() is supported. \H produces a literal H, \" produces a literal ".

More format codes may be added in the future, as demanded by the users of this extension. This may come in the form of either a more complete implementation of PHP's format codes, or additional "x" codes.

The format of the time parameter is identical to the one used by PHP's function strtotime(). It supports both absolute and relative dates, such as "December 11" and/or "+10 hours", which can be used for timezone translation. See also the GNU tar manual for more information.

Examples

• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Monday 4 March 2024" (!error: the comma in this case should not be there)
• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Saturday 12 October 2024" (32 days ago)
• Template:Ft gives "15:06" (6 hours later than UTC)
• Template:Ft gives "14:15"
• Template:Ft gives "06/2023" (17 months ago)

In combination with user-specified date formatting:

• Template:Ft gives "Sunday 4 March 2007"
• Template:Ft gives "Sunday 2007-03-04"

Both give the user-specified format; the two are different if no preference has been specified.

Be careful when piping links:

• Template:Ft gives "Sunday March2007uSun, 04 Mar 2007 00:00:00 +00003112 2007f March 2007"

Use quotes to surround the link code:

• Template:Ft gives "Sunday Fourth of March 2007"

Range

The range of proper functioning is 01 January 1970 00:00:01 through 19 January 2038 03:14:07, or 1 through <math>2^{31}-1</math> seconds after the start of 1970 (the Year 2038 problem). For arbitrary dates that may exceed this range, use date computing templates such as m:Template:dowa (backlinks, edit) instead.

Dates before 1901 give an error message, dates between 1901 and 1970 even give (perhaps depending on the server) a wrong result (!):

• Template:Xpd1Template:Xpd/
• Template:Xpd1Template:Xpd/

Incomplete dates

• Template:Evd (not a year but a time: today, 20:07)
• Template:Evd (19:97 is not a valid time, therefore interpreted as year, giving the current date and time in that year)
• Template:Evd (19:67 is not a valid time, therefore interpreted as year; this gives a date that is out of range which is changed to the start of the valid range)
• Template:Evd (start of the month)
• Template:Evd (today's day and time, of the given month and year)
• Template:Evd (today's day, of the given month and year, at 0 hours)
• Template:Evd (specified date of the current year)

February 29

Caution should be taken with February 29, as {{#time:j|February 29}} will vary with the year. For example

• Template:Ft gives 1
• Template:Ft gives 29

Timezones

Give UTC for a specified time, expressed in time zone UTC-3:

• Template:Evd
• Template:Evd

Give the UTC 3 hours ago:

• Template:Evd

Give the UTC 3 hours before a specified time expressed as UTC:

• Template:Evd

Give the UTC 3 hours before a specified time expressed in time zone UTC-3:

• Template:Evd

Thus "-0300" and "-3" add 3 hours, while "-3 hours" subtracts them.

#rel2abs:

Template:Ft converts a relative path to an absolute path.

Template:Ft
Template:Ft

A relative path is a path starting with '/', './', '../'. or is containing '/../' or '/.' or is simply the strings '..' or '.'.
If a base path is given, is should be defined in an absolute syntax.

Example:

• If standing in Help:Foo/bar and is calling Template:Ft, the result will be Help:Foo/baz
• If standing in Help:Foo and is calling Template:Ft, the result will be baz
• If standing in Help:Foo and is calling Template:Ft, the result will be
• If calling Template:Ft, the result will be Help:Bar/baz
• If calling Template:Ft, the result will be Help:Foo/baz

There is no checks if the path do exist, for that you might use Template:Ft in combination:

Template:Ft gives '..' does not exist

Template:Ft gives '.' exist

#titleparts:

{{ #titleparts: pagename | n_of_segments | starting_from }}
returns n_of_segments slash-separated segments of pagename, starting from the specified starting segment.

• if starting_from is omitted, it is considered to be equal 1
• namespace part of pagename is converted into localized namespace name

Examples with one numeric parameter:

• Template:Evd
• Template:Evd
• Template:Evd
• Template:Evd
• Template:Evd

Examples with two numeric parameters:

• Template:Evd

This gives two parts of the title, starting at the second part. Likewise:

• Template:Evd
• Template:Evd

Examples with negative parameters (which means "counting from the right"):

• Template:Evd
• Template:Evd

Introduced in r22711, fixed to allow negative parameters in r28708. See also bug 6067.

#iferror:

{{#iferror:expression|error|success}} returns error if the expression contains a <strong class="error"> as generated by #expr, #ifexpr, #time, #rel2abs, and some other MediaWiki situations (such as recursive depth and template loop checks). This is most useful in catching bad input passed to such parserfunctions. For example:

• {{#iferror:{{#expr:1+1}}|bad input|valid expression}} gives valid expression
• {{#iferror:{{#expr:1+Z}}|bad input|valid expression}} gives bad input

The last two parameters are also optional. If the success parameter is omitted, then the expression is returned on success. If the error parameter is also omitted, then no output is generated on error, and expression is returned on success.

• {{#iferror:{{#expr:1+1}}|bad input}} gives 2
• {{#iferror:{{#expr:1+Z}}|bad input}} gives bad input
• {{#iferror:{{#expr:1+1}}}} gives 2
• {{#iferror:{{#expr:1+Z}}}} gives

Thus:

• {{#iferror:wikitext|alternative}} means "render wikitext if it is correct, and otherwise alternative".
• {{#iferror:wikitext}} means "render wikitext if it is correct".

Note: this functionality replaces a bug in the older preprocessor allowing #switch to catch expression errors.

See also: r29774, r29775, r29877.

Caveats

Substitution

Applying "subst:" to a parser function works, provided that there is no space between "subst:" and "#". For details see Help:Substitution. Note that unless a technique like optional substitution is used, substituting a template which uses a parser function does not replace that parser function with its result. This is often undesirable.

See also the previous section.

Tables

Currently wiki pipe table syntax doesn't work inside conditionals, but there are some workarounds.

• Hide the pipe from parser functions by putting it in a template, e.g. m:Template:! (backlinks, edit).
• Use html style table syntax instead of wiki style table syntax. NB: $wgUserHtml must be true (this has since been removed, and thus should not need to be set to 'true' - check if it is relevant for your version). This may not work without setting $wgUseTidy=true;.
• See also Help:Table, completely empty rows or columns are not displayed. Empty cells could be also transformed into dummy &nbsp; cells on pages not affected by 5569.

Note that "|" and "=" were always tricky within templates, this is no new issue.

If all else fails, try setting $wgUseTidy=true; in your LocalSettings.php.

useTidy

If you decide to use this, you will need to download the HTML tidy programme from http://tidy.sourceforge.net/.

Expressions

• div is not integer division and is redundant, use / (slash) for real divisions.
• mod uses PHP's % operator, which is different from modulo-operators in all other programming languages, see also m:Template:mod (backlinks, edit) and 6068.
• mod sometimes returns wrong results for the same input values, see 6356 and /MOD10000. Update: values less than 1E+12 are apparently not affected.
• Valid #expr: results like 1.0E-7 were not supported as #expr: input:

  {{#expr:1.0E-7}} yields 1.0E-7 (works now)

• Under certain conditions round 0 results in -0 instead of 0. For an expression x using 0+(x) fixes this oddity.

Newlines and spaces

Newlines and spaces are stripped from the start and end of parameters of all parser functions. In cases where these matter, e.g. in wikitable syntax, for conditionals use m:Template:if (backlinks, edit) as a workaround.

See also Help:Newlines and spaces.

Code execution

Oddly, the page to which #ifexist is applied (i.e. the page whose existence is the condition) is registered as link target of a link from the page with #ifexist. (See bug #12019.)

See also Template:Ml.

Installation

Download all 5 of these files and put them in a new directory called ParserFunctions in your extensions directory.

• Expr.php
• ParserFunctions.php
• ParserFunctions.i18n.php
• ParserFunctions.i18n.magic.php
• SprintfDateCompat.php

If you don't have php5 use these files instead (older revision):

• Expr.php
• ParserFunctions.php

Or, if you have svn, just do:

svn checkout http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ParserFunctions

Then put the following at the end of your LocalSettings.php:

require_once( "$IP/extensions/ParserFunctions/ParserFunctions.php" );

If you get errors such as "Warning: require_once(/extensions/ParserFunctions/ParserFunctions.php) [function.require-once]: failed to open stream:", you should substitute the line for:

require_once( 'extensions/ParserFunctions/ParserFunctions.php' );

You can also browse the code tree here:

• ParserFunctions in MediaWiki SVN

Troubleshooting

The Current version of ParserFunctions requires php5 to function.

INSTALLATION WARNING: MediaWiki: 1.9.1, PHP: 5.1.2-Debian-0.1~sarge1 (apache2handler) function ctype_alpha not available, had to add the following to Expr.php

if ( !function_exists('ctype_alpha') ) {
   function ctype_alpha($string) {
       //if ( !preg_match('|[^\pL]|', $string) )
       /* Warning: preg_match() [function.preg-match]: Compilation failed: PCRE does not support 
       \L, \l, \N, \P, \p, \U, \u, or \X at offset 3 in 
       /.../extensions/ParserFunctions/Expr.php on line 6
       */
       /* alternative: */ // 
       if ( !preg_match('|[^A-Za-z]|', $string) )
           return true;
       else
           return false;
   }
}

If you are using Gentoo Linux's portage system to install php, be sure to have the "ctype" USE flag set for dev-lang/php to avoid the above error.

Bugs

In version 1.6 and 1.7 if a user has the Cite.php extension already installed, an error is created when running ParserFunctions, "Unknown datatype in hooks for ParserClearState", a simple fix has been found by editing Cite.php. ]

1.12.0

If all ParserFunctions evaluate to false, you should check the existence of the global variable:

$wgExpensiveParserFunctionLimit = 100;

It defines the maximum amount of ParserFunctions-calls in one page.

1.11.0

I found that the files above didn't work and that I needed the latest from the svn trunk
http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ParserFunctions/

1.8 and up

All the ParserFunctions work under 1.8 and up, also in the localised forms.

1.7

All the ParserFunctions work under 1.7, but only in English. However, the extension may cause problems when used together with the Cite extension; cf. [2]. For the #time parser functions to work, you must also download SprintfDateCompat.php to the extensions/ParserFunctions directory.

1.6

When including the ParserFunctions in 1.6, some notices may be shown. Removing the following line (line 10) in ParserFunctions.php fixes the problem:

$wgHooks['LanguageGetMagic'][]       = 'wfParserFunctionsLanguageGetMagic';

Or alternatively adding the default language to the header function on line 169 may solve the problem:

function wfParserFunctionsLanguageGetMagic( &$magicWords, $langCode='en' ) {

For the #time parser functions to work, you must also download SprintfDateCompat.php to the extensions/ParserFunctions directory. But actually that won't fix the problem.

If you're not planning to support #time, you may find removing this line helps avoid an error in the ParserClearState call chain:

$wgHooks['ParserClearState'][] = array( &$wgExtParserFunctions, 'clearState' );

Most ParserFunctions (except #if, which does not work at all) work just as well on MediaWiki 1.6, but the syntax of ParserFunctions is without the '#' character. If you want to use the '#' character, find this section of ParserFunctions.php:

 $wgParser->setFunctionHook( 'expr', array( &$wgExtParserFunctions, 'expr' ) );
 $wgParser->setFunctionHook( 'if', array( &$wgExtParserFunctions, 'ifHook' ) );
 $wgParser->setFunctionHook( 'ifeq', array( &$wgExtParserFunctions, 'ifeq' ) );
 $wgParser->setFunctionHook( 'ifexpr', array( &$wgExtParserFunctions, 'ifexpr' ) );
 $wgParser->setFunctionHook( 'switch', array( &$wgExtParserFunctions, 'switchHook' ) );
 $wgParser->setFunctionHook( 'ifexist', array( &$wgExtParserFunctions, 'ifexist' ) );

Then, replace it with this:

 $wgParser->setFunctionHook( '#expr', array( &$wgExtParserFunctions, 'expr' ) );
 $wgParser->setFunctionHook( '#if', array( &$wgExtParserFunctions, 'ifHook' ) );
 $wgParser->setFunctionHook( '#ifeq', array( &$wgExtParserFunctions, 'ifeq' ) );
 $wgParser->setFunctionHook( '#ifexpr', array( &$wgExtParserFunctions, 'ifexpr' ) );
 $wgParser->setFunctionHook( '#switch', array( &$wgExtParserFunctions, 'switchHook' ) );
 $wgParser->setFunctionHook( '#ifexist', array( &$wgExtParserFunctions, 'ifexist' ) );

A simple fix for #if in this version -

Replace:

 function ifHook( &$parser, $test = '', $then = '', $else = '' ) {
  if ($test !== '') {

on line 57 with:

 function ifHook( &$parser, $test = '', $then = '', $else = '' ) {
  if ( (string)$test !== '' ){

Although the above fix doesn't appear to work on PHP 4.3.9

If you find some template responses are being unexpectedly wrapped in <pre></pre>

I saw this problem in 1.6.10 using the workarounds here and worked around it by making sure all results from ParserFunction callbacks were trimmed. If a result had a leading space character, then that portion of the template would be wrapped in pre tags. Couldn't figure out what part of the parser was doing this. But force trimming might be a potential workaround based on your needs.

Alteration and localization

The file ParserFunctions.i18n.php contains the localization for the parserfunctions. Adding more may be done by editing it according to the following guidelines.

In the latest MediaWiki versions, a new case for the language code should be added to function efParserFunctionsWords, for example:

        $words['fr'] = array(
	    'expr'       => array( 0, 'calcul',        'expr' ),
            'if'         => array( 0, 'si',            'if' ),
            'ifeq'       => array( 0, 'si-similaire',  'ifeq' ),
            'ifexpr'     => array( 0, 'si-calcul',     'ifexpr' ),
            'switch'     => array( 0, 'achemine',      'switch' ),
	    'default'    => array( 0, '#default' ); // same
            'ifexist'    => array( 0, 'si-existe',     'ifexist' ),
	    'time'       => array( 0, 'temps',         'time' ),
	    'rel2abs'    => array( 0, 'rel-a-abso',    'rel2abs' ),
	    'titleparts' => array( 0, 'part-titre',    'titleparts' ),
        );

• Please note that every hook established in function wfSetupParserFunctions must have an associated magic-words statement for it to work. Failure to associate a magic word may result in PHP warning messages (see bug #10166).

This method may not work on older version. Alternatively, hooks may be established in function wfSetupParserFunctions, as follows.

// fr
$wgParser->setFunctionHook( '#calcul', array( &$wgExtParserFunctions, 'expr' ) );
$wgParser->setFunctionHook( '#si', array( &$wgExtParserFunctions, 'ifHook' ) );
$wgParser->setFunctionHook( '#si-similaire', array( &$wgExtParserFunctions, 'ifeq' ) );
$wgParser->setFunctionHook( '#si-calcul', array( &$wgExtParserFunctions, 'ifexpr' ) );
$wgParser->setFunctionHook( '#achemine', array( &$wgExtParserFunctions, 'switchHook' ) );
$wgParser->setFunctionHook( '#si-existe', array( &$wgExtParserFunctions, 'ifexist' ) );	
$wgParser->setFunctionHook( '#temps', array( &$wgExtParserFunctions, 'time' ) );	

• Tested on MediaWiki 1.6.10

See also

• Special:Expandtemplates (evaluate functions)

• Help pages
  • Calculation
  • Magic words
  • Template
  • Newlines and spaces - shows how in branching newlines and spaces are preserved.
• Similar extensions
  • mw:Extension:ParserFunctions (extended)
  • mw:Extension:MathStatFunctions
  • mw:Extension:VariablesExtension
  • mw:Extension:StringFunctions
  • mw:Extension:DynamicFunctions
  • Category:Templates using ParserFunctions
  • mw:Extending wiki markup#Parser functions
  • mw:Extension:LoopFunctions, bugzilla:2357 - loop functionality
  • mw:Extension:Control Structure Functions

• Discussions
  • Discussion about the ParserFunctions in the Wikitech-l list archive