Question

$str = 'foooo'; // <- true; how can I get 'foo' + 'oo' ?
$words = array(  
  'foo',
  'oo'
);

What’s the fastest way I could find out if $str starts with one of the words from the array, and split it if it does?

Answer 1

Using $words and $str from your example:

$pieces = preg_split('/^('.implode('|', $words).')/', 
             $str, 0, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);

Result:

array(2) {
  [0]=>
  string(3) "foo"
  [1]=>
  string(2) "oo"
}