wp-admin/includes/class-wp-filesystem-base.php:529Writes a string to a file.
$filestring$contentsstring$modeint|falseoptionalfalsebool public function put_contents( $file, $contents, $mode = false ) { return false; }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-base.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.