PHP variables, strings, and curly braces

For the last couple of days we had a number arguments at work about what is the best way to surround a complex PHP variable inside a double-quoted string.  More specifically, should the sigil ($, dollar sign) be on the inside of the braces or on the outside.  Consider an example:

# my way
echo "Result: ${blah['something']}\n";
# the highway
echo "Result: {$blah['something']}\n";

While considering a number of examples, there seems to be no difference – both ways work.  We’d still need to pick one for consistency reasons though.  And I, as an ex-Perl programmer, was suggesting that we should use the dollar sign on the outside of the expression.  This how I remember it being in Perl (and PHP originated from Perl) .  This is how I am used to it.  And this is how makes most sense to me – a dollar sign immediately warns the programmer that the variable is ahead.

However, after consulting PHP documentation, I was proved wrong.  It is said that both ways often work, but it is much safer to use the dollar sign on the inside.  The manual page even provides a few examples where the dollar on the outside won’t work (such in case with objects).

While this is just a small thing to know and get used to, it still looks annoying to me.