Question

I am looking to create a php script that detects twitter style hashtags from a chunk of text. So it would search for #then_a_word.

Answer 1

Using a regex and preg_match_all(), you could have something like this :

$str = <<<STR
this is a string
with a #tag and
another #hello one
STR;

$matches = array();
if (preg_match_all('/#([^\s]+)/', $str, $matches)) {
  var_dump($matches[1]);
}

Which gives the following output :

array
  0 => string 'tag' (length=3)
  1 => string 'hello' (length=5)

And, if you need to do a bit more manipulations on those, you should take a look at the PCRE Functions section of the manual : there are some others that might help you.