What's the fastest way of concatenating strings in PHP?

[RLSTorrents]

I want to combine two variables together:\[code\]$var1 = 'Welcome ';\[/code\]\[code\]$var2 = $_SESSION['UserName'];\[/code\]Which of these will work faster? Code sample 1:\[code\]$var3 = $var1.$var2;\[/code\]Or code sample 2:\[code\]$var3 = "$var1$var2";\[/code\]