Constants in PHP:

A constant is an identifier for a simple value they are same as variables. Value of a constant cannot change or undefined during the execution of script. A constant name should start with a letter or underscore sign.

Constants are case sensitive. Constants are like variables but they do not need “$” sign for declaration. Constants are automatically global for the script.

To define or declare a constant you have to use “define ()” function. The define() function takes three parameters:

  • First parameter defines the name
  • Second parameter defines the value
  • Third parameter is optional in it we pass the case sensitivity in it

Naming Convention:

By naming convention the identifier must be in uppercase and the name of constants start with a letter or underscore and followed by any number, letter or underscore. Always be sure when you naming a constant because you can not change it at run time.

Example:

This example is without case sensitivity parameter and it will give an error on browser because we didn’t set the case sensitivity

Example:

This example is with case sensitivity parameter means it will also give the output of “welcome” because we set the case sensitivity to true.

 

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