wp-admin/includes/class-wp-filesystem-direct.php:546Creates a directory.
$pathstring$chmodint|falseoptionalfalse$chownstring|int|falseoptionalfalse$chgrpstring|int|falseoptionalfalsebool public function mkdir( $path, $chmod = false, $chown = false, $chgrp = false ) { // Safe mode fails with a trailing slash under certain PHP versions. $path = untrailingslashit( $path ); if ( empty( $path ) ) { return false; } if ( ! $chmod ) { $chmod = FS_CHMOD_DIR; } if ( ! @mkdir( $path ) ) { return false; } $this->chmod( $path, $chmod ); if ( $chown ) { $this->chown( $path, $chown ); } if ( $chgrp ) { $this->chgrp( $path, $chgrp ); } return true; }Introduced in 2.5.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-admin/includes/class-wp-filesystem-direct.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.