php - convert to 3-digit hex color code

Question

I've been using 3-digit hex color values in CSS for a long time: #fff, #999, #069, etc. I can see how the repeating letters/numbers are merged to create a 3-digit hex color code, but I don't fully understand the pattern to be able to write a converter in PHP. Is there documentation for this?

Edit: Oh, perhaps my question wasn't clear. I need to know how some of the 6-digit hex color values are converted to 3-digits. xxxxxx (ffffff) and xxyyzz (006699) – these are the only two patterns, correct?

Answer 1

To convert a 3-character hex code into a 6 character one, you need to repeat each character:

$hex = '#fff';
$hex6 = '#' . $hex[1] . $hex[1] . $hex[2] . $hex[2] . $hex[3] . $hex[3];

If you want to convert it to decimal you can use the hexdec function