AFAIK, there is nothing in PHP that really requires double quotes, and I never use them when writing my own code. But it is mostly a matter of personal preference.

The thing to avoid is using double quotes on a static string. Don't write "Name: " . $name because your wasting processing power. Either do it "Name: $name" or 'name: ' . $name. Either way is acceptable, but you should pick one and use it consistantly.

It seems silly, but I've run across quite a bit of PHP code that mixes it. I have often see "Name: " . $name . "/n" in code*. My habit is define "/n" as a global constant and write 'Name: ' . $name . LF.

Jay

* Or even uglier stuff. 'The name ' . "is $name /n" and 'Name: ' . "$name" . "/n" are both terribly akward.