I suppose that the problem is in ALL PHP versions.

from PHP manual:
---
mixed str_replace ( mixed search, mixed replace, mixed subject [, int &count])
---


If `subject' is a nested array the return is strange (at least unexpected)

For example, next pice of code:
<?php
$x = array ( 'abc', 'xayz',
        array('ddddadddd ', ' fffffffffff ' )
        );
$y=str_replace('a','A',$x);
print_r($y);
?>


I'm expecting as output:
Array
(
    [0] => Abc
    [1] => xAyz
    [2] => Array
        (
            [0] => ddddAdddd 
            [1] =>  fffffffffff 
        )

)

But, the output is:
Array
(
    [0] => Abc
    [1] => xAyz
    [2] => ArrAy
)

I thnik that str_replace should do a recursive call, with type checking.

For now I've solve the problem in my own way:
// for nested arrays as `subject' looks like str_replace has wrong return
function my_str_replace($search, $replace, $mixed)
{
        if (is_string($mixed))
                return str_replace($search, $replace, $mixed );
        if(is_array($mixed))
        {
                foreach($mixed AS $key=>$value)
                         $mixed[$key] = my_str_replace($search, $replace, $value);
                return $mixed;
        };
        // non interesting types
        return $mixed;
}