Common interview questions for PHP outsourcing companies

Share some common PHP interview questions:

1. What modules does the complete mall system include?

Products, promotions, orders, membership modules, permission modules, reports, and advertisements.

2.PHP operating mode: CGI, FAST-CGI, CLI, ISAPI, APACHE module.

Different web servers use different operating modes to run php.
Apache: apache
NGINX: FAST-CGI
IIS: ISAPI
CLI mode: does not run in the web server, but runs in the command line.
CGI mode: Common Gateway Interface.

3.What is php thread safety and non-thread safety? the difference? How to choose?

If the program runs in a multi-threaded manner, the characteristics of multi-threading, data sharing, and the use of a lock mechanism can solve the confusion problem that occurs when operating a total resource concurrently. If a lock mechanism is used, it is thread-safe, otherwise It's just not thread safe.

The bottom layer of Fast-cgi is multi-process, and it does not matter whether the thread is safe or not. Conclusion: If a program is run in a multi-threaded manner, thread safety must be considered, otherwise not.

There is no need to consider thread safety under Linux because it is multi-process.
Threads: Variables can be shared between multiple threads.
Process: The memory addresses of multiple processes are completely independent and do not affect each other.

4.php.ini safe_mode configuration impact?

safe_mode is the safe mode. If php is running in safe mode, some functions may fail. The default is off. For example: unlink, mkdir, rmdir, mysql_*, etc.

5.What does stateless http protocol mean?

Every time data is sent or received, the connection is disconnected. Will not maintain status. Those that are always connected are stateful, such as QQ, online games, etc.

6.php data persistence layer? ORM singleton pattern?

php data persistence layer refers to writing data into a database or file, storing it in a device, and persisting it.

ORM (object, relationship, model) is model, and a model is mapped to a data table. As long as you operate the model, you can operate the data table. Many mvc frameworks are ORM mode.

Singleton mode means that a class can only create one object.

7.strcasecmp-Binary safe comparison of strings, what is binary safe?

Binary is not safe: mainly refers to strings. Some strings will have special meaning after being converted into binary, which is no longer the meaning of the original string.
Binary safety: It is safe no matter how you convert it.

8. What are regular expressions POSIX and PCRE?

are two standard regular expressions. Corresponding to two sets of functions of PHP.
PCRE: preg_xxx is now used, with better performance
POSIX: ereg_xxx

9. Single sign-on implementation principle?

After successful login in one program, notify other projects through ajax and request a data to notify the other party to log in as well. What if I send a data packet? Js[ajax], three kinds of data collection and sending in php.