Add GmailFilterBuilder post

source/_posts/2016-07-15-building-gmail-filters-in-php.md

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+---
+layout: post
+title: Building Gmail Filters with PHP
+tags:
+    - php
+    - gmail
+---
+Earlier this week I wrote a small PHP library called [GmailFilterBuilder][0] that allows you to write Gmail filters in PHP and export them to XML.
+
+I was already aware of a Ruby library called [gmail-britta][1] that does the same thing, but a) I’m not that familiar with Ruby so the syntax wasn’t that natural to me - it’s been a while since I wrote any Puppet manifests, and b) it seemed like a interesting little project to work on one evening.
+
+The library contains two classes - `GmailFilter` which is used to create each filter, and `GmailFilterBuilder` that parses the filters and generates the XML using a [Twig][2] template.
+
+## Usage
+
+For example:
+
+```php
+# test.php
+
+require __DIR__ '/vendor/autoload.php';
+
+$filters = [];
+
+$filters[] = GmailFilter::create()
+  ->from(['example@test.com'])
+  ->label('Test')
+  ->archive()
+  ->neverSpam();
+
+print GmailFilterBuilder::build($filters);
+```
+
+In this case, an email from `example@test.com` would be archived, never marked as spam, and have a label of "Test" added to it.
+
+With this code written, and the GmailFilterBuilder library installed via Composer, I can run `php test.php` and have the XML written to the screen.
+
+This can also be written to a file - `php test.php > filters.xml` - which can then be imported into Gmail.
+
+## Twig Extensions
+
+I also added a custom Twig extension that I moved into a separate [twig-extensions][5] library so that I and other people can re-use it in other projects.
+
+It’s a simple filter that accepts a boolean and returns `true` or `false` as a string, but meant that I could remove three ternary operators from the template and replace them with the `boolean_string` filter.
+
+Before:
+
+    {% raw %}{{ filter.isArchive ? 'true' : 'false' }}{% endraw %}
+
+After:
+
+    {% raw %}{{ filter.isArchive|boolean_string }}{% endraw %}
+
+This can then be used to generate output like this, whereas having blank values would have resulted in errors when importing to Gmail.
+
+    <apps:property name='shouldArchive' value='true'/>
+
+## Example
+
+For a working example, see my personal [gmail-filters][3] repository on GitHub.
+
+## Resources
+
+* [The GmailFilterBuilder library on Packagist][4]
+* [My Gmail filters on GitHub][3]
+* [My Twig Extensions on Packagist][5]
+
+[0]: https://github.com/opdavies/gmail-filter-builder
+[1]: https://github.com/antifuchs/gmail-britta
+[2]: http://twig.sensiolabs.org
+[3]: https://github.com/opdavies/gmail-filters
+[4]: https://packagist.org/packages/opdavies/gmail-filter-builder
+[5]: https://packagist.org/packages/opdavies/twig-extensions