doddo

A plugin which adds a shortcode: <code>[gallery_from_regex_matches]</code> in which a regex attribute should be specified. It will then look for matches in the descriptions and titles of all published images in your library, and create a gallery from the matches it finds.
<ul>
<li>Use for example like this <code>[gallery_from_regex_matches regex="lillill" exclude_ids="764"]</code>, and it will generate a gallery of all your pictures of “Lillill”, except the one which has ID 764.</li>
<li>Sometimes it might be advicable to limit the amount of matches. that can be achieved by adding <code>limit</code> to the shortcode. <code>[gallery_from_regex_matches regex="lillill" exclude_ids="764" limit="10"]</code>.</li>
<li>Sometimes you want to make a gallery of “cats” but not “catsup”, but you don’t want to add <a href="https://dev.mysql.com/doc/refman/5.7/en/regexp.html" rel="nofollow ugc">word boundary</a> <code>[[:>:]]</code>, in this case you can <code>exclude_regex=catsup</code>. Then it could look something along the line of <code>[gallery_from_regex_matches regex="cats" exclude_regex="catsup"]</code>.</li>
<li>The same params (except for <code>ids</code>) as for the <code>[media]</code> shortcode can be used (as this plugin calls that shortcodes callback function (<code>gallery_shortcode()</code>) to generate the gallery), so if you want to specify a particular type (style) of gallery from for example your cat pictures , this might do the trick: <code>[gallery_from_regex_matches regex="(cat|kitten)" type="square"]</code>.</li>
<li>The regular expressions follows the <a href="https://dev.mysql.com/doc/refman/5.7/en/regexp.html" rel="nofollow ugc">MySQL Regexp syntax</a></li>
<li>Some characters will per default not work inside of the shortcode, see the “Caveats” section.</li>
<li>There are no bells and whistles for this plugin but it could potentionally be added in the futre.</li>
</ul>
<h3>Caveats</h3>
Since the regex used by the plugin is specified as an attribute value inside of a shortcode, and the <a href="https://codex.wordpress.org/Shortcode_API" rel="nofollow ugc">Shortcode Api</a> disallows the use of certain characters which could be a part of a valid, useful regex, there are some things to consider.
<blockquote>
Attribute values must never contain the following characters: 
 * Square braces: [ ] 
 * Quotes: ” ‘
[ … ] 
 The recommended method of escaping special characters in shortcode attributes is HTML encoding. Most importantly, any user input appearing in a shortcode attribute must be escaped or stripped of special characters.
</blockquote>
<ul>
<li>if in the regex you need to macth a character set <code>[a-z]</code>, then (following the shortcode Api documentation guidline), they need to be encoded. There are two encodings which the plugin accepts: “html” and “base64” </li>
<li>Currently there is no way to encode these things with help of the plugin, although it is planned for a future release, so the regexes must be encoded manually for now’ 
For example, for regex <code>w[0u][0u]ti</code> can be expressed either:</li>
</ul>
With HTML encoding: 
 <code>[gallery_from_regex_matches regex="w&#091;0u&#093;&#091;0u&#093;ti" encoding="html"]</code>
With Base64 encoding: 
 <code>[gallery_from_regex_matches regex="d1swdV1bMHVddGk=" encoding="base64"]</code>
To encode a string to base64, it can be done from the terminal like this: 
 <code>% echo -n "catsup" | base64 
Y2F0c3Vw 
% echo -n Y2F0c3Vw | base64 --decode 
catsup%</code>

Gallery From Regex Matches

Maintain a gallery by including all published images in your library which match a regex (in title or description).

Gallery From Regex Matches vs Photo Gallery by 10Web – Mobile-Friendly Image Gallery