The advanced Content Filter uses Symfony's Expression Language.
This help page includes a summary of [the Symfony's Expression Language documentation page.](https://symfony.com/doc/current/components/expression_language/syntax.html)
## Basics
The advanced content filter matches each post that is about to be displayed against each enabled rule you set.
A rule is a boolean expression that should return either `true` or `false` depending on post variables.
If the expression using a post variables returns `true`, the post will be collapsed and the matching rule name will be displayed above the collapsed content.
A post will be collapsed if at least one rule matches, but all matching rule names will be displayed above the collapsed content.
3. To block every occurence of the word facebook with a space in front and after the word `body matches "//s facebook/s /"`
4. To colapse every post that contains more than 1 image `body matches "/(?:(?:(?:\\[url(?:=.*)?\\])?\\[img(?:=.*)?\\].*\\[\\/img\\]\\s*(?:\\[\\/url\\])?)\\s*){2}/"`
Control characters (e.g. ``\n``) in expressions are replaced with whitespace. To avoid this, escape the sequence with a single backslash (e.g. ``\\n``).
[attachment type='link' url='https://www.eyeem.com/p/120800309' title='Over-compensation Street Night Car Lights Jeep No | EyeEm' image='https://cdn.eyeem.com/thumb/b2f019738cbeef06e2f8c9517c6286a8adcd3a00-1522184820641/640/480']Photo by @[url=https://twitter.com/MrPetovan]MrPetovan[/url][/attachment]</td>
Over-compensation #<a href="https://friendica.mrpetovan.com/search?tag=Street" class="tag" title="Street">Street</a> #<a href="https://friendica.mrpetovan.com/search?tag=Night" class="tag" title="Night">Night</a> #<a href="https://friendica.mrpetovan.com/search?tag=CarLights" class="tag" title="CarLights">CarLights</a> #<a href="https://friendica.mrpetovan.com/search?tag=Jeep" class="tag" title="Jeep">Jeep</a> #<a href="https://friendica.mrpetovan.com/search?tag=NoPeople" class="tag" title="NoPeople">NoPeople</a> #<a href="https://friendica.mrpetovan.com/search?tag=Close" class="tag" title="Close">Close</a>-up <div class="type-link"><a href="https://www.eyeem.com/p/120800309" target="_blank"><img src="https://friendica.mrpetovan.com/proxy/bb/aHR0cHM6Ly9jZG4uZXllZW0uY29tL3RodW1iL2IyZjAxOTczOGNiZWVmMDZlMmY4Yzk1MTdjNjI4NmE4YWRjZDNhMDAtMTUyMjE4NDgyMDY0MS82NDAvNDgw" alt="" title="Over-compensation Street Night Car Lights Jeep No | EyeEm" class="attachment-image"></a><br><h4><a href="https://www.eyeem.com/p/120800309">Over-compensation Street Night Car Lights Jeep No | EyeEm</a></h4><blockquote>Photo by @<a href="https://twitter.com/MrPetovan" class="userinfo mention" title="MrPetovan">MrPetovan</a></blockquote><sup><a href="https://www.eyeem.com/p/120800309">www.eyeem.com</a></sup></div>
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