$re = '/^((?!\bfruit\b).)* # nothing with "fruit" before
( # then, either:
# 1. fruit apple, followed by things that are not "fruit", followed by fruit banana, non-fruits, and then fruit cherry, or vice versa
\bfruit\b\ apple((?!\bfruit\b).)*(\bfruit\b\ banana((?!\bfruit\b).)*fruit\ cherry|fruit\ cherry((?!\bfruit\b).)*fruit\ banana)
|
# 2. Same with banana at the beginning
fruit\ banana((?!\\\\bfruit\b).)*(fruit\ apple((?!\bfruit\b).)*fruit\ cherry|fruit\ cherry((?!\bfruit\b).)*fruit\ apple)
|
# 3. And with cherry
fruit\ cherry((?!\bfruit\b).)*(fruit\ apple((?!\bfruit\b).)*fruit\ banana|fruit\ banana((?!\bfruit\b).)*fruit\ apple)
)
((?!\bfruit\b).)*$ # no more fruit/sx';
$str = 'fruit apple
some other config line
############
fruit banana
fruit cherry
other config 1
other config';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php