PHP one-time request lifecycle

original text ：http://www.nowamagic.net/librarys/veda/detail/1287

We've never turned it on manually PHP Related processes of , It is coming along with Apache Started by .PHP adopt mod_php5.so Module and Apache Connected to a （ To be specific, it is SAPI, Server application programming interface ）.

PHP There are three modules in total ： kernel 、Zend engine 、 And the extension layer .

• PHP The kernel is used to process requests 、 File stream 、 Error handling and other related operations ;
• Zend engine （ZE） To convert source files to machine language , Then run it on the virtual machine ;
• The extension layer is a set of functions 、 Class libraries and streams ,PHP Use them to perform specific actions .

such as , We need to mysql Extend to connect MySQL database ; When ZE Several extensions may need to be connected when executing the program , At this time ZE Give control to extension , Return after processing specific tasks ; Last ,ZE Return the result of program running to PHP kernel , It then sends the results to SAPI layer , Final output to browser .

In-depth discussion

The real internal operation process is not so simple . The above process is only a simplified version , Let's dig deeper , Look what happened behind the scenes .

Apache After starting ,PHP The interpreter starts .PHP There are two steps in the startup process of ：

• The first step is to initialize some environment variables , This will be throughout SAPI Play a role in the life cycle ;
• The second step is to generate some variable settings only for the current request .

PHP Start the first step

I don't know what the first and second steps are ？ Don't worry , Let's discuss it in detail next . Let's take a look at the first step , It is also the most important step . Remember that , The first step occurs before any request arrives .

start-up Apache after ,PHP The interpreter starts .PHP Call the of each extension MINIT Method , To make these extensions available . have a look php.ini What extensions are open in the file . MINIT It means “ Module initialization ”. Each module defines a set of functions 、 Class libraries, etc. to handle other requests .

A typical MINIT The method is as follows ：

PHP Start the second step

When a page request occurs ,SAPI Layer gives control to PHP layer . therefore PHP Set the environment variables required to reply to this request . meanwhile , It also creates a variable table , Used to store the execution process Variable names and values generated in .PHP Call the RINIT Method , namely “ Request initialization ”. A classic example is Session Modular RINIT, If in php.ini in To enable the Session modular , That's calling the RINIT Will be initialized $_SESSION Variable , And read it in ;RINIT Method can be seen as a preparatory process , It starts automatically between program execution . A typical RINIT The method is as follows ：

PHP Close the first step

Like PHP It's the same as starting ,PHP There are also two steps to close the . Once the page is executed （ Whether it is executed to the end of the file or exit or die Function abort ）,PHP Will start the cleanup program . It will call each module's RSHUTDOWN Method . RSHUTDOWN To clear the symbol table generated when the program is running , That is to call for each variable unset function .

A typical RSHUTDOWN The method is as follows ：

PHP Close step 2

Last , All requests have been processed ,SAPI It's ready to close ,PHP Start the second step ：PHP Call... For each extension MSHUTDOWN Method , This is the last chance for each module to free memory .

A typical RSHUTDOWN The method is as follows ：

such , Whole PHP The life cycle is over . It should be noted that , Only if the server has no requests “ Start the first step ” and “ Close step 2 ”.