这个php函数调用是否容易受到eval注入？

Given this piece of code:

$func = $_GET['func'];
$argument = $_GET['argument'];
if (function_exists($func) && strcasecmp($func, 'assert') !== 0) {
    $result = $func($argument);
    ....

Is it possible to inject malicious code (for example eval) other than standard php functions given eval() is not recognized as function ?
Thx