Question

Possible Duplicate:
Accessing arrays whitout quoting the key

I noticed there’s a subtle difference… if I were to code this:

echo "Welcome, $_SESSION['username'], you are logged in.";

It will fail at parsing. However if I code like this:

echo "Welcome, $_SESSION[username], you are logged in.";

It works as expected which makes me wonder if single quotes are really necessary? I cannot find anything in PHP documentation showing that effect.

Answer 1

In PHP, a global constant that isn’t defined becomes a string.

Don’t rely on this; always quote your array keys.

However, interpolated into a string, it is fine, as it is already a string.

Konforce makes a good point in the comments about using braces in string interpolation.

If you omit them, don’t quote the key.

If you use them, you must quote the key, otherwise the constant will be looked up.