Constants in PHP are defined by "define" and are unchangeable after that. Common examples of such data include configuration settings such as database username and password, website's base URL, company name, etc. PHP - Constants Types - A constant is a name or an identifier for a simple value. Using a const variable vs. a #define can affect where the data is stored in memory, which may force you to use one or the other. PHP Constants with const.
The variables may change their values during the program execution. Class Constants. There are situations when #define cannot be replaced by const. To define a constant you have to use define() function and to retrieve the value of a constant, you have to simply specifying its name. define i use for global constants.. const i use for class constants.. You cannot define into class scope, and with const you can. Not Real Constants. You have to use the PHP keyword 'const' and initialize it with a scalar value -- boolean, int, float, string (or array in PHP 5.6+) -- right away. Here you can find a nice code examples and practice for Variables and constants. Needless to say, you cannot use const outside class scope. Common examples of such data include configuration settings such as database username and password, website's base URL, company name, etc. Because of this, we cannot change constant primitive values, but we can change the properties of constant objects.

It is to be noted, constants are irrespective of their scope i.e constants are automatically of global scope. Constants differ from normal variables in that you don't use the $ symbol to declare or use them. Constants are by definition unchangeable. It defines a constant reference to a value. Also, with const, it actually becomes a member of the class, with define, it will be pushed to global scope. constant() function: Therefore, such a value must be assigned at the same time that the constant is created. As we know both define() and const are used to declare a constant in PHP script. It is best to stick to using #define for optional compilation of blocks of code (combined with #if, #ifdef, etc). A constant is a variable with a value that cannot be changed by the script. In order to create a constant in PHP, we must use the define() method. There are some rules to write variable names in … PHP Programming Server Side Programming. define i use for global constants.. const i use for class constants.. You cannot define into class scope, and with const you can. Variables: Variable in any programming language is a name given to a memory location that holds a value. Constants differ from normal variables in that you don't use the $ symbol to declare or use them. It is ALWAYS preferable to use const, instead of #define. Unlike with variables, you do not need to have a constant with a $. We will learn about variables, constants and echo statements in detail in this PHP variables tutorial. #define can also be used to replace some text in a program with another text. We should use static name and value with the const statement to initialize constants where the define() function allows variable interpolation and function call while defining constant. Вы можете использовать это только из класса.

The value must be a constant expression, not (for example) a variable, a property, or a function call.