how to use constants in php - Wikitechy https://www.wikitechy.com/interview-questions/tag/how-to-use-constants-in-php/ Interview Questions Wed, 03 Aug 2022 12:03:36 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.4 https://www.wikitechy.com/interview-questions/wp-content/uploads/2025/10/cropped-wikitechy-icon-32x32.png how to use constants in php - Wikitechy https://www.wikitechy.com/interview-questions/tag/how-to-use-constants-in-php/ 32 32 What are the ways to define a constant in PHP ? https://www.wikitechy.com/interview-questions/php/what-are-the-ways-to-define-a-constant-in-php/ https://www.wikitechy.com/interview-questions/php/what-are-the-ways-to-define-a-constant-in-php/#respond Wed, 03 Aug 2022 12:03:36 +0000 https://www.wikitechy.com/interview-questions/?p=4564
  • PHP constants are identifier or name that can’t be changed during the execution of the script except for magic constants, which are not really constants.
  • Constants can never be undefined or changed, they are similar to the variable except once defined.
  • PHP constants follow the same PHP variable rules and it remains constant across the entire program.
  • Conventionally, in uppercase letters PHP constants should be defined and it can be started with an underscore or letter only.
  • PHP constants consists of two types, they are:
    • Using define () function
    • Using const keyword

    • Using define () function

    • In PHP use the define () function to create a constant and it defines constant at run time.
    • In this function name specifies the constant name, value specifies the constant value and case-insensitive specifies whether a constant is case-insensitive.
    • By default, if value is false it means it is case sensitive.

    Sample Code

    <?php    
    define("MESSAGE","Welcome to Wikitechy",true);//not case sensitive    
    echo MESSAGE, "</br>";    
    echo message;    
    ?>

    Output

    Using const Keyword

    • PHP introduces a const keyword to create a constant and it defines constants at compile time.
    • It constructs a language, not a function.
    • The constant defined using const keyword are case-sensitive.

    Sample Code

    <?php      
        define("MSG", "Wikitechy");  
        echo MSG, "</br>";  
        echo constant("MSG");  
        //both are similar  
    ?>

    Output

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