PHP get_defined_constants() Function

The get_defined_constants() function is an inbuilt function in PHP that returns the name of all the constants that are currently defined with their values in the form of an associative array.

Syntax:

get_defined_constants(bool $categorize = false): array

Parameter: This function accepts single parameter that is described below:

• $categorize: This function returns a multidimensional array that contains categories in the keys for the first dimension & constants with their values will be in the second dimension.

Return Value: This function returns an array in the form of keys and values, i.e, key name => value.

Example 1: In the below example, we will be called the get_defined_constants() function and print the associative array. Here, the get_defined_constants prints all constant as well as user-defined constants.

PHP

<?php
define("MY_FIRST_CONSTANT",1);
print_r(get_defined_constants(true)) ;
?>

Output:

Array (
    [Core] => Array
        (
           [E_ERROR] => 1
           [E_RECOVERABLE_ERROR] => 4096
           [E_WARNING] => 2
           [E_PARSE] => 4
           [E_NOTICE] => 8
           [E_STRICT] => 2048
           [E_DEPRECATED] => 8192
           [E_CORE_ERROR] => 16
           [E_CORE_WARNING] => 32
           [E_COMPILE_ERROR] => 64
           [E_COMPILE_WARNING] => 128
           [E_USER_ERROR] => 256
           [E_USER_WARNING] => 512
           [E_USER_NOTICE] => 1024
           [E_USER_DEPRECATED] => 16384
           [E_ALL] => 32767
           [DEBUG_BACKTRACE_PROVIDE_OBJECT] => 1
           [DEBUG_BACKTRACE_IGNORE_ARGS] => 2
        )
   [user] => Array
       (
           [MY_FIRST_CONSTANT] => 1
       )
)

Example 2: In the below example, we will print only user define constant user get_defined_constants() function.

PHP

<?php
define("MY_FIRST_CONSTANT",1);
print_r(get_defined_constants(true)["user"]) ;
?>

Output:

Array
(
   [MY_FIRST_CONSTANT] => 1
)

Reference: https://www.php.net/manual/en/function.get-defined-constants.php