PHP资本化

I not only need to capitalize the first letter in my string but also the 5th.

How would you capitalize the string "RoadAtlanta" properly?

You can refer to chars by their index:

$string[4] = strtoupper($string[4]);

4 in this particular case refers to 5th character. String characters are indexed from 0 as arrays so you can directly refer to characters at particular position.