Faster: Concatenation or double quote?

[Rub]

Does anyone know which is faster? Concatenating strings using single quotes or rather using double quotes?

Ex:

echo 'This is a'.$comment;

or

echo "This is a $comment";

[daynah]

Single quotes since it will print as is rather than evaluate the statement in case there's variables.

[jabba_29]

There were numberous discussions on a similar topic at Devshed

I learnt quite a lot from it..