<?php

$disabled_funcs = [];

// original code
function func ($msg) {
  echo "$msg\n";
}

//The wrapped one:

function _func () {
  global $disabled_funcs;
  $func = substr (__FUNCTION__, 1);
  if (isset($disabled_funcs[$func]))
    throw new Exception ("Function $func is disabled.");
  return call_user_func_array ($func, func_get_args());
}

function disable_func ($name) {
	global $disabled_funcs;
	$disabled_funcs[$name] = 1;
}

function enable_func ($name) {
	global $disabled_funcs;
	if (isset($disabled_funcs[$name]))
		unset ($disabled_funcs[$name]);
}

//Call the function:
_func ("Func not disabled.");
disable_func ("func");
try {
	_func ("Exception will be raised, this will not be displayed");
} catch (Exception $e) {
	echo $e->getMessage() . PHP_EOL;
}
enable_func ("func");
_func ("Func enabled");