Definition of constants in PHP_PHP tutorial

1. Custom constants
* Must be defined using function define()
* Its value cannot be changed after it is defined
* Use the constant name directly when using it. You cannot add $s
in front like a variable. For example: define("PI",3.14); define a constant
$area = PI*R*R; Calculate the area of ​​the circle
        define("URL","http://www.ybldcc.com");
echo "My URL is: ".URL;
2 System constants:
FILE:php program file name
LINE: Number of lines of PHP program file
PHP_VERSION: The version number of the current parser
PHP_OS: The name of the operating system that executes the current PHP version
Author “ITeamsky-Yang Bo’s Technology Space”

http://www.bkjia.com/PHPjc/478666.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/478666.htmlTechArticle1. Custom constants* must be defined using the function define()* and their values ​​cannot be changed after definition* When using it, use the constant name directly. You cannot add $s in front like a variable. For example: define(PI,3.14...