I did say “don’t use “” if you do not need to!” as with all things this needs to be your own best judgment, there are of course caveats such as sacrificing functionality for performance, which in some cases as you say may be a minor gain.

Thanks for the reference material though always appreciated

The reason double quotes is slower, is that the string is parsed. Everything is single quotes is taken literally and thus not parsed. Thus you should not compare the speed, but the functionality of the two. Speed should only be an issue if it really it negatively effects performance. Using double quotes can be very beneficial in that you do not have to concatenate strings together with variables and escapes.

Unless you are working with very huge strings, the performance difference is negligible. Many other factors become important way before that. A good approach is to understand bottlenecks (such as disk), and performance of code. see: http://en.wikipedia.org/wiki/Computational_complexity_theory

Here is a good article on micro-optimization (which is what you’re doing when using single quotes instead of double quotes). Though published in 2006, it still applies today.
http://www.acm.org/ubiquity/views/v7i24_fallacy.html

Anywho congrats on the new edition

You were incorrect with your “this\nstring\nappears\over\nmany\nlines” comment. The correct single quote method would be…

‘this’ . “\n” . ‘string’ . “\n” . ‘appears’ . “\n” . ‘over’ . “\n” . ‘many’ . “\n” . ‘lines’

Or perhaps:

$array = array(‘this’, ‘string’, ‘appears’, ‘over’, ‘many’, ‘lines’);
$string = implode(“\n”, $array);

Although the second one is more elegant I doubt it’s really any good for static text. Feel free to run speed tests though.

cheers
Sean

ps: now a dad!