CodeIgniter Framework-source code Analysis of the entry file index.php

The portal file of the CodeIgniter framework is primarily a configuration development environment, defining directory constants, and loading CI core class core/codeigniter.php.

The source code analysis is as follows:

<?PHP//This file is an entry, and all the files in the later stages are to be executed here. /*-----------------------------------------------* System Environment Configuration Constants * Ability to configure error display levels *-------------------------------------- ---------* By default: * Development//Development environment reports ALL errors * testing//test environment does not report errors * production//production environment does not report errors*/    Define(' Environment ', ' development '); /** Different error display levels are opened according to environment constants*/    Switch(Environment) { Case' Development ':error_reporting(E_all);  Break;  Case' Testing ': Case' Production ':error_reporting(0);  Break; default:Exit(' app environment settings are wrong. ')); } /**---------------------http://i.cnblogs.com/?postid=3921349&update=1 * System file directory, can be customized *--------------------* By default, the "System" folder is in the same directory as the index.php file. * You can change this path, but the path must be the same as the location of your system files * * Do not need the trailing slash "/"; */     $system _path= ' System '; /**---------------------------------------------------------------* application directory *----------------------------------- ----------------------------* * This folder is where the program is placed, by default the "Application" folder, which can be renamed or relocated to any location on the server. * Details can be accessed: * http://codeigniter.com/user_guide/general/managing_apps.html * * Does not require the trailing slash "/"; * */     $application _folder= ' Application '; /**--------------------------------------------------------------------* This place has a set of user code, I do not know how to find out, I do not write a *------- ------------------------------------------------------------- */
/* *---------------------------------------------------------------* Troubleshoot routing problems with a reliable path *------------------------------ --------------------------------- */     //do you want to run from the command line? ———— correctly set command line (CLI) requests in the current directory    if(defined(' STDIN ')){         chdir(dirname(__file__)); }     if(Realpath($system _path) !==FALSE){         $system _path=Realpath($system _path).‘ /‘; }     //Make sure that the last one is a slash "/";    $system _path=RTrim($system _path, ‘/‘).‘ /‘; //determine if the system directory exists    if( !Is_dir($system _path)){         Exit("Your system directory is not set correctly. Please open the following file reset: ".PathInfo(__file__,pathinfo_basename)); } /**-------------------------------------------------------------------* Set path (directory) constants *--------------------------- ---------------------------------------- */    //gets the current file name, which defines the entry file name    Define(' Self ',PathInfo(__file__,pathinfo_basename)); //php file extension
Using global constants is not recommended    Define(' EXT ', '. php '); //System Catalog Constants    Define(' BasePath ',Str_replace("\\", "/",$system _path)); //Front-end controller path constant, which is the directory of the portal file    Define(' Fcpath ',Str_replace(Self, ",__file__)); //System Core Directory Name
Trim (basepath, '/') removes the "/' ———— trim () function from both ends of the string to remove whitespace characters and other pre-defined characters
The strrchr() function finds the last occurrence of a string in another string and returns all characters from that position to the end of the string
    Define(' Sysdir ',Trim(STRRCHR(Trim(BasePath, '/'), '/'), '/')); //Defining application Directory Constants    if(Is_dir($application _folder)){         Define(' APPPATH ',$application _folder.‘ /‘); }Else{        if( !Is_dir(BasePath.$application _folder.‘ /‘)){             Exit("Your application directory may not be set correctly.") Please open the following file settings: ".Self ); }         Define(' APPPATH ', basepath.$application _folder.‘ /‘); } /**--------------------------------------------------------------------* Loading bootstrap file *------------------------------ -------------------------------------- */
Before you define the environment and define constants, start loading CI core files and start a true CI tour
require_onceBasePath. ' Core/codeigniter '.EXT;/*End of File index.php*//*Location :./index.php*/