magic constants in php - Wikitechy https://www.wikitechy.com/interview-questions/tag/magic-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 magic constants in php - Wikitechy https://www.wikitechy.com/interview-questions/tag/magic-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

    ]]>     https://www.wikitechy.com/interview-questions/php/what-are-the-ways-to-define-a-constant-in-php/feed/ 0     What are Magic Constants in PHP ? https://www.wikitechy.com/interview-questions/php/what-are-magic-constants-in-php/ https://www.wikitechy.com/interview-questions/php/what-are-magic-constants-in-php/#respond Mon, 01 Aug 2022 09:09:07 +0000 https://www.wikitechy.com/interview-questions/?p=4535
  • In PHP magic constants are the predefined constants which is used on the basis of their use.
  • Constants are created by various extensions and there are nine magic constants in the PHP and all of the constant resolved at the compile-time, not like the regular constant which is resolved at run time.
  • In this there are eight magic constants which start and end with double underscores (__), they are.
    • __line__
    • __file__
    • __dir__
    • __function__
    • __class__
    • __method__
    • __namespace__
    • __trait__

    • __line__

    • This type of magic constant returns the current line number of the file.
    • In our program file if we use this magic constant somewhere then this constant will display the line number during compile time.

    Syntax

             __line__

    __file__

    • This type of magic constant return the full path of the executed file with the name of the file.

    Syntax

             __file__

    __dir__

    • This type of magic constant returns the directory of the executed file.

    Syntax

              __dir__

    __function__

    • This type of magic constant returns the name of the function where it is included.

    Syntax

             __function__

    __class__

    • This type of magic constant returns the name of the class where it is included.

    Syntax

    __class__

    __method__

    • This type of magic constant returns the method name where it is included.

    Syntax

           __method__

    __namespace__

    This type of magic constant returns the current namespace where it is included.

    Syntax

           __namespace__

    __trait__

    • This type of magic constant returns the trait name where it is included.

    Syntax

      __trait__

    ]]> https://www.wikitechy.com/interview-questions/php/what-are-magic-constants-in-php/feed/ 0