In PHP 5.3.0, `is_a()` is no longer deprecated, and will therefore no longer throw `E_STRICT` warnings.
To avoid warnings in PHP < 5.3.0, convert all `is_a()` calls to `$var instanceof WP_Class` calls.
`instanceof` does not throw any error if the variable being tested is not an object, it simply returns `false`.
Props markoheijnen, wonderboymusic.
Fixes#25672.
git-svn-id: https://develop.svn.wordpress.org/trunk@31188 602fd350-edb4-49c9-b593-d223f7449a82
* All WordPress files move to a src/ directory.
* New task runner (Grunt), configured to copy a built WordPress to build/.
* svn:ignore and .gitignore for Gruntfile.js, wp-config.php, and node.js.
* Remove Akismet external from develop.svn. Still exists in core.svn.
* Drop minified files from src/. The build process will now generate these.
props koop.
see #24976.
and see http://wp.me/p2AvED-1AI.
git-svn-id: https://develop.svn.wordpress.org/trunk@25001 602fd350-edb4-49c9-b593-d223f7449a82