Unsure on some php code

I'm not a PHP programmer and I have very little experience with PHP in general.

 

However, I've got some code that I believe comes from a php module file. I was wondering if anyone could either explain what it does or provide an equivalent example in a different language (preferably in c or python).

 

sub ASCIItoUnicode
{
    return join('', map {($_, "\0")} split(//, $_[0]));
}

... This isn't homework in any way, shape or form.