$group = "(?P<{$i}_{$name}>" . preg_quote( $syn, '/' ) . ')'; MediaWiki API
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HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <help>
    <module>* list=categorymembers (cm) *
  List all pages in a given category

This module requires read rights
Parameters:
  cmtitle        - Which category to enumerate (required). Must include Category: prefix
                   This parameter is required
  cmprop         - What pieces of information to include
                    ids           - Adds the page ID
                    title         - Adds the title and namespace ID of the page
                    sortkey       - Adds the sortkey used for sorting in the category (hexadecimal string)
                    sortkeyprefix - Adds the sortkey prefix used for sorting in the category (human-readable part of the sortkey)
                    type          - Adds the type that the page has been categorised as (page, subcat or file)
                    timestamp     - Adds the timestamp of when the page was included
                   Values (separate with '|'): ids, title, sortkey, sortkeyprefix, type, timestamp
                   Default: ids|title
  cmnamespace    - Only include pages in these namespaces
                   Values (separate with '|'): 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
                   Maximum number of values 50 (500 for bots)
  cmtype         - What type of category members to include. Ignored when cmsort=timestamp is set
                   Values (separate with '|'): page, subcat, file
                   Default: page|subcat|file
  cmcontinue     - For large categories, give the value retured from previous query
  cmlimit        - The maximum number of pages to return.
                   No more than 500 (5000 for bots) allowed
                   Default: 10
  cmsort         - Property to sort by
                   One value: sortkey, timestamp
                   Default: sortkey
  cmdir          - In which direction to sort
                   One value: asc, desc
                   Default: asc
  cmstart        - Timestamp to start listing from. Can only be used with cmsort=timestamp
  cmend          - Timestamp to end listing at. Can only be used with cmsort=timestamp
  cmstartsortkey - Sortkey to start listing from. Can only be used with cmsort=sortkey
  cmendsortkey   - Sortkey to end listing at. Can only be used with cmsort=sortkey
Examples:
  Get first 10 pages in [[Category:Physics]]:
    api.php?action=query&list=categorymembers&cmtitle=Category:Physics
  Get page info about first 10 pages in [[Category:Physics]]:
    api.php?action=query&generator=categorymembers&gcmtitle=Category:Physics&prop=info
</module>
  </help>
</api>