Technically you can define constants with names that are not valid for variables:<?php// $3some is not a valid variable name// This will not work$3some = 'invalid';// This worksdefine('3some', 'valid');echo constant('3some');?>Of course this is not a good practice, but PHP ha...
<?phpclass ParentClass{ const CONSTANT = 'CONST_PARENT';}class A extends ParentClass{ const CONSTANT = 'CONST_A'; public static function getSelf() { return self::CONSTANT; } public static function getParent() { return parent::CONSTANT; }}echo 'im class A{} and this is my: self CONST...
const CONSTANT_NAME = "constant_value"; Here,const: This is the keyword used to create a constant using the const syntax. CONSTANT_NAME: This is the name of the constant, following the same rules as variables . constant_value: This is the value assigned to the constant. It can be a ...
// Valid constant names define("ONE", "first thing"); define("TWO2", "second thing"); define("THREE_3", "third thing"); define("__THREE__", "third value"); // Invalid constant names define("2TWO", "second thing"); Difference between Constants and Variables in PHP...
4echoConstant;//outputs "Constant" and issues a notice. 5 6define("GREETING","Hello you.",true); 7echoGREETING;//outputs "Hello you." 8echoGreeting;//outputs "Hello you." 9 10?> 常量和变量不同: 常量前面没有美元符号($); 常量只能用define()函数定义,而不能通过赋值语句; ...
4echoConstant;//outputs "Constant" and issues a notice. 5 6define("GREETING","Hello you.",true); 7echoGREETING;//outputs "Hello you." 8echoGreeting;//outputs "Hello you." 9 10?> 常量和变量不同: 常量前面没有美元符号($); 常量只能用define()函数定义,而不能通过赋值语句; ...
Constants are variables whose values, once defined, cannot be changed, and these constants are defined without a $ sign in the beginning. PHP Constants are created using define() function. This function takes two parameters first is the name, and the second is the value of the constant ...
PHP7 高性能开发学习手册(全) 原文:zh.annas-archive.org/md5/57463751f7ad4ac2a29e3297fd76591c 译者:飞龙 协议:CC BY-NC-SA 4.0 前言 PHP 社区在几十年来面临着一个巨大的问题:性能。无论他们拥有多么强大的硬件,最终 P
Assigning a string to a variable is done with the variable name followed by an equal sign and the string: Example $x="John";echo$x; Try it Yourself » String variables can be declared either by using double or single quotes, but you should be aware of the differences. Learn more abou...
Here's the PHP doc entry on the getenv() call to retrieve environment variables. Generally speaking, the difference between a constant and a variable is that one is constant, and the other is, well, variable. :) From the standpoint of writing a program that depends on login string...