It's not legit to error-out for eval, since PHP has all kinds of eval-like things.

For example, PHP has two namespaces for functions: anonymous functions live in the regular variable namespace, so they can be passed around directly. Named (AKA global) functions are completely separate, so we can't pass them around as values. For example:

    $my_anon = function() {};

    function my_named() {}

    // Valid
    array_map($my_anon, []);

    // Invalid
    array_map(my_named, []);

As a workaround, whenever PHP sees a string when it's expecting a function, it will try to find a global function with a name matching the contents of the string. In other words, we can do:

    // Valid
    array_map('my_named', []);

This is basically a weak form of eval: taking a string of PHP code ('my_named') and getting back the value it evaluates to (the my_named function). If you error-out for eval, you have to error-out for this, since the content of strings is runtime information and there's no way you can infer it well enough. For example:

    function smart_replace() {
      $args = func_get_args();
      $func = array_shift($args)? 'str' : 'preg';
      return call_user_func_array("{$func}_replace", $args);
    }

Other eval-like things in PHP include variable property lookups, variable method calls and "variable variables":

    $foo = "hello";

    $object1->$foo = $object2->$foo;  // Sets $object1's "hello" property to $object2's

    $object3->$foo();  // Calls $object3's "hello" method

    $bar = "foo";
    echo $$bar;  // Outputs hello

One interesting fact about these features is that, since they're not as powerful as a real eval, it can often be perfectly safe to supply them with unvalidated user input:

    array_map('str_' . $_GET['string_function'], $my_array);

There's no way we can swap out things like this reliably, and remember that these are not just "crazy uses of eval", they're officially sanctioned ways of working, which in some cases (eg. function names in strings) have no alternatives (short of redefining your own standard library).