Application analysis of PHP short circuit operator

/**
* php short circuit operator
* edit by bbs.it-home.org
*/
mysql_query($sql) or die('Execute failed!');
!file_exists($cache_file) && @update_cache($id);
 file_exists($cwd."/download/".$down_id)||mkdir($cwd."/download/".$down_id,0757)
?>

Instructions: 1. [ or ][ || ][ and ][ && ] are short-circuit operators 2. The or, || operator will check whether the first expression returns "true". If it is "true", the end statement will return "true", otherwise the next expression will be checked. 3. The and, && operator checks whether the first expression returns "false". If it is "false", it ends the statement and returns "false". Otherwise, it checks the second expression.

The above uses the characteristics of short-circuit operators to realize the judgment and execution of conditions.