send the function name with get request and check if is Get value exist
and use call_user_func($functionName)
and if there is parameter with function you can use call_user_func_array($functionName , $pramaters)
`function test()
{
echo "string";
}
if ($_GET['func']) {
$func = $_GET['func'];
call_user_func($func);
}`
you can also use function_exists to enshure if the function exist and this function return False or True
this code Example :
if(function_exists('my_function'))
{
throw new Exception("'my_function' is already defined!");
}
function my_function()
{
// Do the work here
}