header code in vb

[chrispadfield]

this is a snippet from config.php


if (!$header) {
eval("\$header = \"".gettemplate('header')."\";");
} else {
eval("\$header .= \"".gettemplate('header')."\";");
}


i am trying to work out the point of it. It is saying:

- if $header is already set with something, then add the header template to header. if it is not set then make header = header.

Thing is i can't understand the point of it, what is the practical, speed etc difference between what is above and simply


eval("\$header .= \"".gettemplate('header')."\";");


is it the case that


$x = "a";


is faster than


$x .= "a";


?