Php to replace @username with link to twitter account

Question

I assume this is some to do with regex, but it\'s an art all it\'s own - and I need some help.

When we display a story, we store all the text in a varilable - let\'s

Answer 1

$input = preg_replace('/(^|\s)@([a-z0-9_]+)/i',
                      '$1@$2',
                       $input);

See it

It matches a @ which is preceded by whitespace or nothing ( when it is at the beginning).

It can also be shorted using positive lookbehind as:

$input = preg_replace('/(?<=^|\s)@([a-z0-9_]+)/i',
                      '@$1',
                      $input);

Which matches only the twitter name but only if there is space or nothing before that.