As far as language similarities, they're almost identical. The key difference is how loosely typed PHP is, but other than that, it's like I already know everything I'm seeing. Sure they may be used differently, but that's not what I was saying.
They both use curly braces and semicolons. Other than that, they are vastly different languages.
Consider: C++ has no triple-equality or triple-inequality operators (=== and !== respectively) but these are essential to certain types of comparison in PHP, especially when dealing with multiple types. Classes function totally differently in PHP and C++. So do global variables; c.f. the "global" keyword in PHP for instance. PHP has no namespaces. The standard libraries are wildly different in their offerings. PHP has no templates or macros.
And that's without getting into the list of things that the two languages are good for; have fun writing a Direct3D engine in PHP ;-) (And yes, you can write web sites PHP-style in C++ if you really want to use CGI, but it's still painful.)
It's very tempting to look at two languages and see that they use the same squiggly symbols, and assume that they are therefore similar languages. And yet the syntax - those symbols - is basically the least important aspect of any programming language.
To support my argument that syntax is irrelevant, consider multilingual quines and macros that make C look like Pascal. There's also the Lisp family, which via macros (different kind of macros though) can be made to look like virtually any language under the sun.