diff --git a/.travis.yml b/.travis.yml
index 9cbdd66250e30e..dae3085e5b875b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -58,11 +58,7 @@ script:
     fi
   - |
     if [[ "$TRAVISCI" == "phpcs" ]] ; then
-      find . \
-        -not \( -path './node_modules' \) \
-        -not \( -path './vendor' \) \
-        -name '*.php' \
-      | xargs -d'\n' phpcs --standard=phpcs.ruleset.xml -s
+      phpcs
     fi
   - |
     if [[ "$TRAVISCI" == "js" ]] ; then
diff --git a/docs/coding-guidelines.md b/docs/coding-guidelines.md
index fc06a5430f6d7f..d52c747d43c047 100644
--- a/docs/coding-guidelines.md
+++ b/docs/coding-guidelines.md
@@ -78,3 +78,42 @@ Example:
  */
 import VisualEditor from '../visual-editor';
 ```
+
+## PHP
+
+We use
+[`phpcs` (PHP\_CodeSniffer)](https://github.com/squizlabs/PHP_CodeSniffer)
+with the
+[WordPress Coding Standards ruleset](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards)
+to run a lot of automated checks against all PHP code in this project.  This
+ensures that we are consistent with WordPress PHP coding standards.
+
+When making any changes to the PHP code in this project, it's recommended to
+install and run `phpcs` on your computer.  This is a step in our Travis CI
+build as well, but it is better to catch errors locally.
+
+You will need to install `phpcs` version 2.9.x, because the 3.x versions are
+not yet compatible with the WordPress coding standards.  For more information see
+[this issue](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards/issues/718).
+
+The easiest way to get `phpcs` is to download the .phar archive from the latest
+2.9.x release on GitHub:
+[PHP\_CodeSniffer releases](https://github.com/squizlabs/PHP_CodeSniffer/releases).
+
+For example:
+
+```sh
+wget \
+    https://github.com/squizlabs/PHP_CodeSniffer/releases/download/2.9.1/phpcs.phar \
+    -O ~/bin/phpcs
+chmod +x ~/bin/phpcs
+```
+
+(If `~/bin` is not in your `$PATH`, pick another directory that is.)
+
+Then you must install the `WordPress-Coding-Standards` repository and tell
+`phpcs` where it lives.  See instructions here:
+
+https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards#standalone
+
+You should now be able to run `phpcs` from the root directory of this project.
diff --git a/phpcs.ruleset.xml b/phpcs.xml
similarity index 76%
rename from phpcs.ruleset.xml
rename to phpcs.xml
index db418a3af44071..5dbac182d815b8 100644
--- a/phpcs.ruleset.xml
+++ b/phpcs.xml
@@ -1,10 +1,16 @@
 <?xml version="1.0"?>
-<ruleset name="WordPress Coding Standards for Plugins">
-	<description>Generally-applicable sniffs for WordPress plugins</description>
+<ruleset name="WordPress Coding Standards for Gutenberg Plugin">
+	<description>Sniffs for WordPress plugins, with minor modifications for Gutenberg</description>
 
 	<rule ref="WordPress-Core" />
 	<rule ref="WordPress-Docs" />
 
+	<arg value="s"/>
+	<arg name="extensions" value="php"/>
+
+	<file>gutenberg.php</file>
+	<file>./phpunit</file>
+
 	<!-- The plugin entry point already has a file comment, I promise -->
 	<rule ref="Squiz.Commenting.FileComment.Missing">
 		<exclude-pattern>gutenberg.php</exclude-pattern>