Single or Double Quotes?

Sometimes people use double quotes in PHP to avoid having to use the period to separate code. For example, you could write:

"I have a $color shirt on today";

Faster however is not always better. A better way to write this code would be:

'I have a ' .$color. ' shirt on today';

Phrasing your code in the second method will result in less chance of error messages, or problems with other programmers deciphering your code.