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PHP replace multiple words

So I want to remove everything but some words. I want to keep for an example "car", "circle" and "roof". But remove everything else in a string.

Let's say the string is "I have a car with red one circle at the roof". I wantr to remove everything but "car", "circle" and "roof".

I know there's this one:

$text = preg_replace('/\bHello\b/', 'NEW', $text);

But I can't figure out how to do it with multiple words. I've done this below, but it does the opposite.

$post = $_POST['text'];
$connectors = array( 'array', 'php', 'css' );

$output = implode(' ', array_diff(explode(' ', $post), $connectors));

echo $output;
Solution 
  • <?php
$wordsToKeep = array('car', 'circle', 'roof');
$text = 'I have a car with red one circle at the roof';

$words = explode(' ', $text);
$filteredWords = array_intersect($words, $wordsToKeep);

$filteredString = implode(' ', $filteredWords);

    $filteredString would then equal car circle roof.

    See http://php.net/manual/en/function.array-intersect.php