Introduction

PmWiki's markup translation engine is handled by a set of rules; each rule searches for a specific pattern in the markup text and replaces it with some replacement text. Internally, this is accomplished by using PHP's "preg_replace" function.

Rules are added to the translation engine via PmWiki's Markup() or Markup_e() functions, which look like

Markup($name, $when, $pattern, $replace); # if no evaluation is needed, or if PHP < 5.5
Markup($name, $when, $pattern, $replace_function); # if evaluation is needed

# DEPRECATED, will not work as of PHP 7.2
Markup_e($name, $when, $pattern, $replace); # if evaluation is needed and 5.5<=PHP<=7.1

• $name is a unique name (a string) given to the rule
• $when says when the rule should be applied relative to other rules
• $pattern is the pattern to be searched for in the markup text
• $replace is what the pattern should be replaced with.
• $replace_function is the name of the function which should be called with the match, and should return the replacement.

For example, here's the code that creates the rule for ''emphasized text'' (in scripts/stdmarkup.php):

Basically this statement says to create a rule called "em" to be performed with the other "inline" markups, and the rule replaces any text inside two pairs of single quotes with the same text ($1) surrounded by <em> and </em>.

Sequence in which rules are applied

The first two parameters to Markup() are used to specify the sequence in which rules should be applied. The first parameter provides a name for a rule -- "em" in the example above. We could've chosen other names such as "''", or even "twosinglequotes". In general PmWiki uses the markup itself to name the rule (i.e., PmWiki uses "''" instead of "em"), but to keep this example easier to read later on we'll use a mnemonic name for now.

The second parameter says that this rule is to be done along with the other "inline" markups. PmWiki divides the translation process into a number of phases:

  _begin      start of translation
    {$var}    Page Text Variables happen here.
  fulltext    translations to be performed on the full text            
  split       conversion of the full markup text into lines to be processed
  directives  directive processing
  inline      inline markups
  links       conversion of links, url-links, and WikiWords     
  block       block markups
  style       style handling       
  _end        end of translation

This argument is normally specified as a left-angle bracket ("before") or a right-angle bracket ("after") followed by the name of another rule.

Thus, specifying "inline" for the second parameter says that this rule should be applied when the other "inline" rules are being performed. If we want a rule to be performed with the directives -- i.e., before inline rules are processed, we would specify "directives" or "<inline" for the second parameter.

{$var} and (:if ...:) conditionals

A significant rule in terms of ordering is "{$var}" which substitutes variables -- if you say "<{$var}" then your markup will be processed before variables are substituted whereas if you say ">{$var}" then your markup will be processed after variables are substituted. This happens before conditional (:if...:) expressions, which is why page text variables are processed even if they are defined inside (:if false:).

Markup regular expression definition

The third parameter is a Perl-compatible regular expression. Basically, it is a slash, a regular expression, another slash, and a set of optional modifiers.

The example uses the pattern string "/''(.*?)''/", which uses ''(.*?)'' as the regular expression and no options. (The regular expression says "find two single quotes in succession, then as few arbitrary characters as are needed to make the match find something, then two additional single quotes in succession"; the parentheses "capture" a part of the wikitext for later use.)

Replacement text

The fourth parameter is the replacement text that should be inserted instead of the marked-up wikitext. You can use $1, $2, etc. to insert the text from the first, second etc. parenthesised part of the regular expression.

In the example, we have "<em>$1</em>", which is an <em>, the text matched by the first parentheses (i.e. by the .*? section of the pattern), and </em>.

Here's a rule for @@monospaced@@ text:

and for a [:comment ...:] directive that is simply removed from the output:

Okay, now how about the rule for '''strong emphasis'''? We have to be a bit careful here, because although this translation should be performed along with other inline markup, we also have to make sure that the rule for ''' is handled before the rule for '', because ''' also contains ''. The second parameter to Markup() can be used to specify the new rule's relationship to any other rule:

This creates a rule called "strong", and the second parameter "<em" says to be sure that this rule is processed before the "em" rule we defined above. If we wanted to do something after the "em" rule, we would use ">em" instead. Thus, it's possible to add rules at any point in PmWiki's markup translation process in an extensible manner. (In fact, the "inline", "block", "directives", etc., phases above are just placeholder rules used to provide an overall sequence for other rules. Thus one can use "<inline" to specify rules that should be handled before any other inline rules.)

If you want to disable available markup just call e.g.:

PmWiki's default markup rules are defined in the scripts/stdmarkup.php file. To see the entire translation table as the program is running, the scripts/diag.php module adds "?action=ruleset", which displays the set of defined markup rules in the sequence in which they will be processed. You can see it at CustomMarkup?action=ruleset. You must first enable the action by setting $EnableDiag = 1 in your configuration file.

Other common examples

Define a custom markup to produce a specific HTML or Javascript sequence

Suppose an admin wants to have a simple "(:example:)" markup that will always produce a fixed HTML string in the output, such as for a webring, Google AdSense display, or Javascript. The Markup() call to do this would be:

Markup('example', 'directives',
  '/\\(:example:\\)/',
  Keep("<div class='example'><p>Here is a 
    <a target='_blank' href='http://www.example.com'>link</a> to
    <em>example.com</em></p></div>") );

• The first argument is a unique name for the markup ("example").
• The second argument says to perform this markup along with other directives.
• The third argument is the pattern to look for "(:example:)".
• The fourth argument is the HTML that "(:example:)" is to be replaced with. We use the Keep() function here to prevent the output from being further processed by PmWiki's markup rule -- in the above example, we don't want the http://www.example.com url to be again converted to a link.

Define a markup to call a custom function that returns content

For older PHP versions (< 7.2) an 'e' option on the $pattern parameter causes the $replace parameter to be treated as a PHP expression to be evaluated instead of replacement text. To avoid using the deprecated e/ parameter, a markup to produce a random number between 1 and 100 might now look like:

Markup('random', 'directives',
  '/\\(:random:\\)/',
  "MyRandomFunction");
function MyRandomFunction() {
  return rand(1, 100);
}

This calls the PHP built-in rand() function and substitutes the directive with the result. Any function can be called, including functions defined in a local customization file or in Cookbook recipes.

Arguments can also be passed by using regular expression capturing parentheses, thus

Markup('randomargs', 'directives',
  '/\\(:random (\\d+) (\\d+):\\)/',
  "MyRandomFunction");
function MyRandomFunction($m) {
  return rand($m[1], $m[2]);
}

will cause the markup (:random 50 100:) to generate a random number between 50 and 100.

For a PmWiki function to help with parsing arbitrary sequences of arguments and key=value pairs, see Cookbook:ParseArgs.

Migration to PHP 5.5 and Markup_e()

Since PHP version 5.5, the /e evaluation modifier is deprecated and some hosting providers don't allow its use.

Recent versions of the PmWiki core (2.2.58 and newer) allow new ways to define markup rules without being dependent on the /e eval modifier. The historical ways to define markup rules are not removed and work, but may be incompatible with PHP 5.5 installations.

Note: whether your replacement pattern needs evaluation or not, you must use Markup() and not Markup_e(). The latter is deprecated and should no longer be used for new recipes and customizations, and old recipes using Markup_e should be upgraded to the new format.

The examples below all require PmWiki 2.2.58 (2013-12-25) or newer but the latest version is recommended.

The following is acceptable for PHP 5.5+ (compatible with PmWiki 2.2.58+, will also work in PHP 5.4 and older)

• Markup($name, $when, $pattern, $replace);
  • $pattern can no longer have an "/e" modifier
  • $replace can be a function name (callback) which will be called with the array of matches as argument
  • instead of a string, the fourth parameter can be a definition of an anonymous function (note you can use anon functions this way since PHP 5.3.0+).
• Markup_e($name, $when, $pattern, $replace); DEPRECATED, should no longer be used

Examples:

• For PHP 5.4 and older, this was acceptable:

  Markup('randomargs', 'directives',
    '/\\(:random (\\d+) (\\d+):\\)/e',
    "rand('$1', '$2')"
    );
• For PHP 5.5 and newer, $replace is callback, we call Markup():

  Markup('randomargs', 'directives',
    '/\\(:random (\\d+) (\\d+):\\)/',
    "MyRandom"
    );
  function MyRandom($m) { # $m = matches
    return rand($m[1], $m[2]); # note "return" is used, unlike before
  

  This will also work in PHP 5.4 and older

Other example:

• PHP 5.4 or older:

  Markup('Maxi:','<links',
    "/\\b([Mm]axi:)([^\\s\"\\|\\[\\]]+)(\"([^\"]*)\")?/e",
    "Keep(LinkMaxi(\$pagename,'$1','$2','$4','$1$2'),'L')"
    );
  
• PHP 5.5 or newer, PmWiki 2.2.58+, $replace is a function name:

  Markup('Maxi:','<links',
    "/\\b([Mm]axi:)([^\\s\"\\|\\[\\]]+)(\"([^\"]*)\")?/",
    "LinkMaxi"
    );
  function LinkMaxi($m) {
    extract($GLOBALS['MarkupToHTML']); # to get $pagename
    # do stuff with $m[1], $m[2], etc.
    return Keep($out, 'L');
  }
  

  This will also work in PHP 5.4 and older
• $replace can also be a callback function, we call Markup():

  Markup('Maxi:','<links',
    "/\\b([Mm]axi:)([^\\s\"\\|\\[\\]]+)(\"([^\"]*)\")?/",
    "CallbackMaxi"
  );
  function CallbackMaxi($m) {
    extract($GLOBALS["MarkupToHTML"]); # to get $pagename
    return Keep(LinkMaxi($pagename,$m[1],$m[2],$m[4],$m[1].$m[2]),'L');
  }
  

  This will also work in PHP 5.4 and older

The above may seem complicated, but it is actually simpler to use your own callback function:

Markup('mykey', 'directives', 
  '/\\(:mydirective (.*?) (.*?):\\)/i',
  'MyFunction'
);
function MyFunction($m) {
  extract($GLOBALS["MarkupToHTML"]);

  # ... do stuff with $m (the matches), drop PSS() ...

  return $out; # or return Keep($html);
}

If you have any questions about the new way to define custom markup, you can ask us at the talk page or on the mailing lists.

FAQ

SDV($HideDiscussion, 0); 	#define var name
Markup('hideDiscussion', '<{$var}',
 '/\\(:nodiscussion:\\)/', 'setHideDiscussion'); 
function setHideDiscussion() { 
  global $HideDiscussion; 
  $HideDiscussion = true;
}