PHPde bir sabit değişkeni nasıl bildirebilirsiniz?

Defining a constant variable in PHP is a straightforward process. A constant is a value that cannot be changed during the execution of a script. Once a constant is defined, its value remains the same throughout the script.
There are two ways to define a constant in PHP: using the define() function and using the const keyword.
Using the Define() Function:
The define() function is used to define a constant variable in PHP. It takes two arguments: the name of the constant and its value.
Example:
```
define(\"PI\", 3.14);
echo PI; // Output: 3.14
```
In the above example, we define a constant named “PI” and give it a value of 3.14. We can then use the constant in our code by simply calling its name.
Using the Const Keyword:
The const keyword is another way to define a constant in PHP. Unlike the define() function, the const keyword can only be used inside a class or when declaring a global constant.
Example:
```
const MAX_VALUE = 100;
echo MAX_VALUE; // Output: 100
```
In the above example, we define a constant named “MAX_VALUE” inside a class and give it a value of 100. We can then use the constant in our code by simply calling its name.
Note that once a constant variable is defined, its value cannot be changed during the execution of a script. Attempting to change the value of a constant variable will result in a fatal error.
In conclusion, defining a constant variable in PHP is a simple process that can be done using either the define() function or the const keyword. Constants are useful for storing values that remain constant throughout the execution of a script.