wp-includes/plugin.php:845Get the filesystem directory path (with trailing slash) for the plugin __FILE__ passed in.
$filestringstringfunction plugin_dir_path( $file ) { return trailingslashit( dirname( $file ) );}Introduced in 2.8.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/plugin.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.