Detailed explanation of how PHP outputs all variables/constants/modules/functions/class codes

Example of PHP outputting all variables, constants, modules, functions, and classes of the current process

1. get_defined_vars (PHP 4 >= 4.0.4, PHP 5) — Get by Array of all defined variables
array get_defined_vars (void)
This function returns a multidimensional array containing a list of all defined variables, including environment variables , server variables and user-defined variables.

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
$b = array(1,1,2,3,5,8);
$arr = get_defined_vars();
// 打印 $b
print_r($arr["b"]);
// 打印所有服务器变量
print_r($arr["_SERVER"]);
// 打印变量数组的所有可用键值
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

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
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

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
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 passed-in parameter (module name) must be lowercase

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
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 and their values ​​in an associative array
array get_defined_constants ([ bool $categorize = false ] )

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
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)

<?php
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
//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());
?>

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