How do you use constants in php?

Constants are simple pieces of data which cannot be changed during PHP script execution. It is useful for storing data which should remain unchanged, like a maximum or minimum value of a variable, etc.

Before first use, constant should be defined: ...

define("MY_MAX_VALUE", 505);

... After this, you can use it:

...

if ($my_variable < MY_MAX_VALUE)

{

... (some code here)

}

...