Another tricky preg_match

Question

Just need to see if a paragraph contains a "stop word", the stop words are in an array below.

I had the formula as:

$pattern_array = array("preheat", "minutes", "stir", "heat", "put", "beat", "bowl", "pan");

    foreach ($pattern_array as $pattern) {
      if (preg_match('/'.$pattern.')/i', $paragraph)) {
        $stopwords = 1;
      }
    }

Which works well enough but for short words like 'pan' a word like 'panko' is identified as a stop word.

So the regex would be something like it has to have a space before it or be the start of a new line and either end in a full stop/space/comma/(other non character objects).

Also how could I tell php to exit the loop as soon as a stop word is identified?

Thanks guys, slowing learning regex as I go!

Answer 1

Haven't tried this, but \b should be the character group you're looking for. From the PHP manual:

 \b   word boundary

Your code would then look something like this:

$pattern_array = array("preheat", "minutes", "stir", "heat", "put", "beat", "bowl", "pan");

foreach ($pattern_array as $pattern) {
  if (preg_match('/\b'.$pattern.'\b/i', $paragraph)) { // also removed the ')'
    $stopwords = 1;
    break; // to exit the loop
  }
}

Edit: seems people are better off using \b, so changed this accordingly

Answer 2

you need to add \b (which stands for word boundary) to your regex like this:

'/\b'.$pattern.'\b/i'

You seem to have a typo in your code, because either you have a literal closing bracket (and don't match parts of the words) or you have an open closing bracket.

Answer 3

Use \b(preheat|minutes|stir|heat|put|bowl|pan)\b as your regex. That way, you only need one regex (no looping necessary), and by using the \b word boundary assertions, you make sure that only entire words match.

Answer 4

1. You can use "\b" to check for word boundaries. A word boundary is defined as the boundary between a word character and a non-word character. word-characters are letters, numbers, and underscore.

2. You can do it all at one go, by using "|":

$stopwords = preg_match('/\\b(preheat|minutes|stir|heat|..other words..|pan)\\b/i', $paragraph)