wp-includes/pomo/streams.php:118$input_stringstring$chunk_sizeintarray public function str_split( $input_string, $chunk_size ) { if ( ! function_exists( 'str_split' ) ) { $length = $this->strlen( $input_string ); $out = array(); for ( $i = 0; $i < $length; $i += $chunk_size ) { $out[] = $this->substr( $input_string, $i, $chunk_size ); } return $out; } else { return str_split( $input_string, $chunk_size ); } }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/pomo/streams.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.