std::chrono is used in C to process time, including obtaining the current time, measuring execution time, operation time point and duration, and formatting analysis time. 1. Use std::chrono::system_clock::now() to obtain the current time, which can be converted into a readable string, but the system clock may not be monotonous; 2. Use std::chrono::steady_clock to measure the execution time to ensure monotony, and convert it into milliseconds, seconds and other units through duration_cast; 3. Time point (time_point) and duration (duration) can be interoperable, but attention should be paid to unit compatibility and clock epoch (epoch)

ToaccessenvironmentvariablesinPHP,usegetenv()orthe$_ENVsuperglobal.1.getenv('VAR_NAME')retrievesaspecificvariable.2.$_ENV['VAR_NAME']accessesvariablesifvariables_orderinphp.iniincludes"E".SetvariablesviaCLIwithVAR=valuephpscript.php,inApach

PHPhasthreecommentstyles://,#forsingle-lineand/.../formulti-line.Usecommentstoexplainwhycodeexists,notwhatitdoes.MarkTODO/FIXMEitemsanddisablecodetemporarilyduringdebugging.Avoidover-commentingsimplelogic.Writeconcise,grammaticallycorrectcommentsandu

WhensettingupMySQLtables,choosingtherightdatatypesiscrucialforefficiencyandscalability.1)Understandthedataeachcolumnwillstore—numbers,text,dates,orflags—andchooseaccordingly.2)UseCHARforfixed-lengthdatalikecountrycodesandVARCHARforvariable-lengthdata

When using PHP preprocessing statements to execute queries with IN clauses, 1. Dynamically generate placeholders according to the length of the array; 2. When using PDO, you can directly pass in the array, and use array_values to ensure continuous indexes; 3. When using mysqli, you need to construct type strings and bind parameters, pay attention to the way of expanding the array and version compatibility; 4. Avoid splicing SQL, processing empty arrays, and ensuring data types match. The specific method is: first use implode and array_fill to generate placeholders, and then bind parameters according to the extended characteristics to safely execute IN queries.

The key steps to install PHP on Windows include: 1. Download the appropriate PHP version and decompress it. It is recommended to use ThreadSafe version with Apache or NonThreadSafe version with Nginx; 2. Configure the php.ini file and rename php.ini-development or php.ini-production to php.ini; 3. Add the PHP path to the system environment variable Path for command line use; 4. Test whether PHP is installed successfully, execute php-v through the command line and run the built-in server to test the parsing capabilities; 5. If you use Apache, you need to configure P in httpd.conf

The steps for setting MySQL semi-synchronous replication are as follows: 1. Confirm the version supports and load the plug-in; 2. Turn on and enable semi-synchronous mode; 3. Check the status and operation status; 4. Pay attention to timeout settings, multi-slave library configuration and master-slave switching processing. It is necessary to ensure that MySQL 5.5 and above versions are installed, rpl_semi_sync_master and rpl_semi_sync_slave plugins, enable corresponding parameters in the master and slave library, and configure automatic loading in my.cnf, restart the service after the settings are completed, check the status through SHOWSTATUS, reasonably adjust the timeout time and monitor the plug-in operation.

The basic syntax of PHP includes four key points: 1. The PHP tag must be ended, and the use of complete tags is recommended; 2. Echo and print are commonly used for output content, among which echo supports multiple parameters and is more efficient; 3. The annotation methods include //, # and //, to improve code readability; 4. Each statement must end with a semicolon, and spaces and line breaks do not affect execution but affect readability. Mastering these basic rules can help write clear and stable PHP code.