In order to create a constant in PHP, we must use the define() method. In Javascript one can define variables using the keywords var, let or const.. var a=10; let b=20; const PI=3.14;.

Class Constants.

#define can also be used to replace some text in a program with another text. PHP const is a language construct where the define() is a function. It is possible to define constant values on a per-class basis remaining the same and unchangeable. It is to be noted, constants are irrespective of their scope i.e constants are automatically of global scope. Constants are very useful for storing data that doesn't change while the script is running. Variables on the other hand are changeable and one can perform operations on them.
A constant is a variable with a value that cannot be changed by the script. That's because const is treated by the compiler and #define by the preprocessor.

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. A valid constant name must start with an alphabet or underscore and requires no ‘$’. By default, a constant is case-sens Unlike with variables, you do not need to have a constant with a $. Here you can find a nice code examples and practice for Variables and constants. Constants Besides properties and methods in the body of the class can also be defined constants. The keyword const is a little misleading.. The constants keep always the same value.

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. Because of this, we cannot change constant primitive values, but we can change the properties of constant objects.

Needless to say, you cannot use const outside class scope. PHP provides two methods for creating constants: the const modifier and the define() function. Syntax: There are some rules to write variable names in …

Syntax: The TL;DR version. const are always case sensitive, whereas define() allows you to define case insensitive constants by passing true as the third argument: 3. A constant is an identifier (name) for a simple value. For example, #define can take parameters (See this for example). Вы можете использовать это только из класса.

Therefore, such a value must be assigned at the same time that the constant is created. Constants are very useful for storing data that doesn't change while the script is running. As of PHP 5.3 there are two ways to define constants: Either using the const keyword or using the define() function: [crayon-5ed5da7c342fd963711701/] The fundamental difference between those two ways is that const defines constants… const variables will (usually) be stored in SRAM, along with all other variables. Constants are by definition unchangeable. The variables may change their values during the program execution. - Syntax: const CONSTANT_NAME The main difference between properties and constants is that the constant value cannot be changed once it is set. До PHP 5.3, const не может использоваться в глобальной области. PHP Constants with const. It is possible to define constant values on a per-class basis remaining the same and unchangeable.

You can also use the function constant() to read a constant's value if you wish to obtain the constant's name dynamically.

Here you can find a nice code examples and practice for Variables and constants. Also, with const, it actually becomes a member of the class, with define, it will be pushed to global scope. Since PHP 5.6 const constants can also be arrays, while define() does not support arrays yet. The constants keep always the same value. The value must be a constant expression, not (for example) a variable, a property, or a function call. Constants defined using this construct is always case sensitive. Вы можете использовать это только из класса. We will learn about variables, constants and echo statements in detail in this PHP variables tutorial. Constants differ from normal variables in that you don't use the $ symbol to declare or use them. Constants differ from normal variables in that you don't use the $ symbol to declare or use them.
Constants may not be redefined or undefined once they have been set. It is ALWAYS preferable to use const, instead of #define. Also, with const, it actually becomes a member of the class, with define, it will be pushed to global scope. You can say that variables are containers for any type of values.

It defines a constant reference to a value.

A constant value cannot change during the execution of the script.

Common examples of such data include configuration settings such as database username and password, website's base URL, company name, etc.