How to invert preg_match_all php - php

Question

How can I invert pre_match_all, so the output of the code below is "you" instead of "hello" and "world"?
$text1 = array ('you', 'hello', 'WORLD');
$text2 = "Hello world";
//preg_match
foreach ($text1 as $text) {
if (preg_match_all("~\b$text\b~i", $text2, $match)) {
$match = $match[0];
echo "<pre>";
print_r($match);
echo "</pre>";
}
}

Answer 1

Split the string by non-word characters and use array_udiff with strcasecmp as callback:
$words = ['you', 'hello', 'WORLD'];
$str = "Hello world toto";
print_r(array_udiff($words, preg_split('~\W+~', $str), 'strcasecmp'));
// Array
// (
// [0] => you
// )

Answer 2

You don't need preg_match_all(), preg_match() is enough (it returns 1 if it finds a match, 0 otherwise).
You also don't need the matching substrings, it's enough to know if it found a word in the text or not.
$words = array('you', 'hello', 'WORLD');
$text = "Hello world";
// Filter $words, keep only the items that are not present in $text
$missing = array_filter(
$words,
function($w) use ($text) {
// return TRUE when $w is not in $text
return preg_match('/\b'.preg_quote($w, '/').'\b/i', $text) == 0;
});
print_r($missing);

Answer 3

You can use str_ireplace which is case insensitive version of str_replace.
If you replace with nothing, what is left is what is not in $text2.
$text1 = array ('you', 'hello', 'WORLD');
$text2 = "Hello world";
$text2 = explode(" ", $text2);
echo str_ireplace($text2, "", implode("",$text1));
// you
https://3v4l.org/T8o2l
Another method would be to use array_diff and preg_grep.
Preg_grep matches with regex the words from text2 in text1 case insensitive and returns what is matching.
Then I use array_diff to see what is different from $text1 and the return from preg_grep.
$text1 = array ('you', 'hello', 'WORLD');
$text2 = "Hello world";
$text2 = explode(" ", $text2);
Var_dump(array_diff($text1, preg_grep("/" . Implode("|", $text2) . "/i", $text1)));
https://3v4l.org/WOuh6