PHP str_replace with file_put_contents, interacting with cache

Not sure why, but the problem is here, this is the last line in my PHP, through the global.php file, I save the cleaned data in the cache folder. In the situation below, I am saving it as "s & pcurrent". In my release, I get a "+" which I don't want that from the original content. Likewise, I created str_replace to get rid of the + with a space ''

However this doesn't work, I have to format it somehow. Any tips? Many thanks.

file_put_contents(globalVars::$_cache_dir . "s&pcurrent", str_replace('+', ' 
', $ret_[0]);