Introduction to the method of PHP outputting all variables and constants of the current process

 echo '';
 $b = array(1,1,2,3,5,8);
 $arr = get_defined_vars();
 // print $ b
 print_r($arr["b"]);
 // Print all server variables
 print_r($arr["_SERVER"]);

 // Print all available key values ​​​​of the variable array
 print_r(array_keys(get_defined_vars ()));
?>

2. get_defined_functions (PHP 4 >= 4.0.4, PHP 5) — Get all defined functions array get_defined_functions (void) //void means empty and does not require any parameters

 echo '';
 function foo()
 {
 echo "This is my function foo";
 }
 $arr = get_defined_functions();
 print_r($ arr);

?>

3. get_loaded_extensions (PHP 4, PHP 5) — Get all available modules

 echo '';
 print_r(get_loaded_extensions());
?>

4. get_extension_funcs (PHP 4, PHP 5) — Get the available functions of the specified module array get_extension_funcs (string $module_name) This function returns all available functions of the specified module. The parameters passed in (module names) must be lowercase

 echo '';
 print_r(get_extension_funcs("gd"));
 print_r(get_extension_funcs("xml"));
?>

5. get_defined_constants (PHP 4 >= 4.1.0, PHP 5) — Get the names of all constants in an associative array and their values array get_defined_constants ([ bool $categorize = false ] )

 echo '';
 define("MY_CONSTANT", 1);
 print_r(get_defined_constants(true));
?>

6. get_declared_classes (PHP 4, PHP 5) — Get an array consisting of the names of defined classes array get_declared_classes ( void )

 echo '';
 //define classone
 class classone { }

 //define classtwo
 class classtwo { }

 //This will show X classes ( built-ins, extensions etc) with
 //classone and classtwo as the last two elements

 print_r(get_declared_classes());

 //define classthree
 class classthree { }

 //...and four
 class classfour { }

 //Shows the same result as before with class three and four appended
 print_r(get_declared_classes());
?>