What is PHP Constant?

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In PHP, a constant is a name or identifier for a value that cannot change during the execution of a script. Constants are similar to variables, but unlike variables, they cannot be changed once they are defined. Constants are typically used for storing values that are meant to remain constant throughout the execution of a PHP script, such as configuration settings, fixed values, or values that should not be altered by mistake.

Here's how you define a constant in PHP:

php code

define("CONSTANT_NAME", "constant_value");

"CONSTANT_NAME" is the name of the constant, and it is case-sensitive.

"constant_value" is the value assigned to the constant.

For example, if you want to define a constant for the value of pi, you can do it like this:

php code

define("PI", 3.14159265);

Once a constant is defined, you can use it throughout your script by simply referencing its name:

php code

echo PI; // Outputs: 3.14159265

Constants have some key characteristics:

Constants are global: Once defined, they can be used anywhere in the script, including inside functions and classes.

Constants do not use the $ symbol: Unlike variables, constants are referenced without the $ symbol.

Constants are case-sensitive: The names of constants are case-sensitive by default. That means PI and pi would be treated as two different constants.

Constants cannot be redefined: Once defined, a constant's value cannot be changed or redefined elsewhere in the script.

Here's an example of how constants might be used in a PHP script:

php code

define("SITE_NAME", "My Website");

define("VERSION", "1.0");

echo "Welcome to " . SITE_NAME . " (Version " . VERSION . ")";

This code defines two constants, SITE_NAME and VERSION, and then uses them to display a welcome message with the site's name and version number.

Comments

  1. AnonymousSeptember 27, 2023 at 4:27 AM

    I'm grateful for your contribution of valuable information.

    ReplyDelete

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