Backporting PHP 7 string type declaration to PHP 5

example.php

<?php

// in coercive mode

// PHP 7 func
function foo(string $bar)
{
    return $bar;
}

// PHP 5 func equiv
function baz($qux)
{
    if (!is_string($qux)) {
        if (is_int($qux) || is_float($qux) || is_bool($qux)) {
            $qux = (string) $qux;
        } elseif (is_object($qux) && method_exists($qux, '__toString')) {
            $qux = $qux->__toString();
        } else {
            throw new Exception;
        }
    }

    return $qux;
}

class Test {function __toString() {return 'a';}}

var_dump(foo(1)); 
var_dump(foo(1.1));
var_dump(foo(true));
var_dump(foo(new Test));
var_dump(foo(new StdClass)); // error
var_dump(foo(null)); // error
var_dump(foo(fopen(__FILE__, 'r'))); // error

var_dump(baz(1));
var_dump(baz(1.1));
var_dump(baz(true));
var_dump(baz(new Test));
var_dump(baz(new StdClass)); // error
var_dump(baz(null)); // error
var_dump(baz(fopen(__FILE__, 'r'))); // error