php - looking for a regex to find and reorder a string

Question

i'm looking for a regex to find the CSS shortcut character pattern form top-right-bottom-left (ie: 10px 20px 40px 0) and swap item number 2 with item number 4 (swap left and right). preferably this regex should be able to identify px values as well as % and em, and will take into account that 0 can be present without any identifier.

Answer 1

You can use a regex like this:

(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)

And implement it like so:

$subject = '10px 20% 40px 0';
$result = preg_replace('/(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)s+(d+(?:px|em|%)?)/i', '$1 $4 $3 $2', $subject);
echo $result; // Prints: 10px 0 40px 20%