Sort array items in PHP so that it is not case sensitive to letters

Question

When I use sort($topics) I get something along the lines of:

1. Apple
2. Green
3. Zebra
4. grass

In this example, "grass" starts with a lower case g but ends up after "Zebra" which has a capital letter.

How do I make it so that it sorts it where it ignores whether the word starts with capitals or not?

1. Apple
2. Green
3. grass
4. Zebra

Answer 1

Call usort() as usort($topics, 'strnatcasecmp').

strcasecmp would do the job, too, but strnatcasecmp will also sort properly when you have numbers in your string.