Manual:Parser functions

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Tag Extensions

Parser Functions

[edit] Parser functions

Parser functions, available since 1.7, provide a way to integrate much more closely than tag extensions with templates and other parser features. There is an embryonic parser function feature in 1.6, but using it is not recommmended, due to the differences in API and syntax.

Seems to work well in 1.6.8 with the suggested mods as per ParserFunctions.

Compare with tag hook extensions, which are expected to take unprocessed text and return HTML. There is virtually no integration with the rest of the parser; for example, the output of an extension cannot be used as a template parameter. Expanding templates within extension tags is possible, but must be done manually -- an error-prone process which changes from version to version.

The typical syntax for a parser function is:

{{ #functionname: param1 | param2 | param3 }}

Creating a parser function is slightly more complicated than creating a tag hook, because the function name must be a "magic word" -- a kind of keyword that supports aliases and localisation. Below is an example of an extension that creates a parser function.

<?php
 
# Define a setup function
$wgExtensionFunctions[] = 'efExampleParserFunction_Setup';
# Add a hook to initialise the magic word
$wgHooks['LanguageGetMagic'][]       = 'efExampleParserFunction_Magic';
 
function efExampleParserFunction_Setup() {
        global $wgParser;
        # Set a function hook associating the "example" magic word with our function
        $wgParser->setFunctionHook( 'example', 'efExampleParserFunction_Render' );
}
 
function efExampleParserFunction_Magic( &$magicWords, $langCode ) {
        # Add the magic word
        # The first array element is case sensitive, in this case it is not case sensitive
        # All remaining elements are synonyms for our parser function
        $magicWords['example'] = array( 0, 'example' );
        # unless we return true, other parser functions extensions won't get loaded.
        return true;
}
 
function efExampleParserFunction_Render( &$parser, $param1 = '', $param2 = '' ) {
        # The parser function itself
        # The input parameters are wikitext with templates expanded
        # The output should be wikitext too
        return "param1 is $param1 and param2 is $param2";
}
?>

With this extension enabled,

* {{#example:hello | hi }}

produces:

param1 is hello and param2 is hi

As with tag extensions, $parser->disableCache() may be used to disable the cache for dynamic extensions.

To return unparsed HTML output instead of wikitext output using a parser function, use:

return array($output, 'noparse' => true, 'isHTML' => true);

Here is the documentation for setFunctionHook, copied from the comments in the code in includes/Parser.php:

function setFunctionHook( $id, $callback, $flags = 0 )

Parameters:

string $id - The magic word ID
mixed $callback - The callback function (and object) to use
integer $flags - Optional, set it to the SFH_NO_HASH constant to call the function without "#".

Return value: The old callback function for this name, if any

Create a function, e.g. {{#sum:1|2|3}}. The callback function should have the form:

function myParserFunction( &$parser, $arg1, $arg2, $arg3 ) { ... }

The callback may either return the text result of the function, or an array with the text in element 0, and a number of flags in the other elements. The names of the flags are specified in the keys. Valid flags are:

found: The text returned is valid, stop processing the template. This is on by default.
nowiki: Wiki markup in the return value should be escaped
noparse: Unsafe HTML tags should not be stripped, etc.
noargs: Don't replace triple-brace arguments in the return value
isHTML: The returned text is HTML, armour it against wikitext transformation

[edit] Naming

When choosing a name without a hash character (number sign, "#"), note that transclusion of a page with a name starting with that function name followed by a colon is no longer possible. In particular, avoid function names equal to a namespace name. In the case that interwiki transclusion [1] is enabled, also avoid function names equal to an interwiki prefix.