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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() function, which looks like
For example, here's the code that creates the rule for
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
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 -- "
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 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
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.
The example uses the pattern string
The fourth parameter is the replacement text that should be inserted instead of the marked-up wikitext. You can use
In the example, we have
Here's a rule for
and for a
Okay, now how about the rule for
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 "
Other common examples
Suppose an admin wants to have a simple "
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>") );
Define a markup to call a custom function that returns content
An 'e' option on the
Markup('random', 'directives', '/\\(:random:\\)/e', "rand(1, 10)");
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.
Arguments can also be passed by using regular expression capturing parentheses, thus
Markup('randomargs', 'directives', '/\\(:random (\\d+) (\\d+):\\)/e', "rand('$1', '$2')");
will cause the markup
Note: Be very careful with the /e modifier in regular expressions; malicious authors may be able to pass strings that cause arbitrary and undesirable PHP functions to be executed.
For a PmWiki function to help with parsing arbitrary sequences of arguments and key=value pairs, see Cookbook:ParseArgs.