PHP preg_split while keeping delimiter at the start of array element

I'm new to regex, and I want to split a string on a delimiter, while keeping that delimiter at the beginning of each array element. I tried it unsuccessfully, and came up with:

    $str = 'LOTS OF STUFF AND SOME MORE STUFF AND SOME OTHER STUFF';
    $matches = preg_split('/(\ AND)/', $str, null, PREG_SPLIT_DELIM_CAPTURE);

This puts the delimiter as its own element :

[0]=>"LOTS OF STUFF"
[1]=>" AND"
[2]=>" SOME MORE STUFF"
[3]=>" AND"
[4]=>" SOME OTHER STUFF"

But I wanted to keep the delimiter at the beginning of the element:

[0]=>"LOTS OF STUFF"
[1]=>" AND SOME MORE STUFF"
[2]=>" AND SOME OTHER STUFF"

I thought maybe I could do it trying to use a look-behind, but then I was losing the delimiter again:

    $matches = preg_split('/(?<=\s)AND/', $str, null, PREG_SPLIT_DELIM_CAPTURE);

[0]=>"LOTS OF STUFF"
[1]=>" SOME MORE STUFF"
[2]=>" SOME OTHER STUFF"

Would love some help, thanks!!

Solution

Use lookahead assertion ((?=)) to split at the string positions followed by AND:

$str = 'LOTS OF STUFF AND SOME MORE STUFF AND SOME OTHER STUFF';
$matches = preg_split('/ (?=AND)/', $str); 
var_dump($matches);
/*
array(3) {
  [0]=>
  string(13) "LOTS OF STUFF"
  [1]=>
  string(19) "AND SOME MORE STUFF"
  [2]=>
  string(20) "AND SOME OTHER STUFF"
}
*/

Demo. This code removes whitespace preceding AND; if it's not what you want, just get rid off the whitespace in the regex.