In this post I'll provide you with three different methods of doing what you ask for. I actually recommend using the last snippet, since it's easiest to comprehend as well as being quite neat in code.

How to get the matching elements of an array

There is a function dedicated for just this purpose, preg_grep. It will take a regular expression as first parameter, and an array as the second.

See the below example:

$haystack = array (
  'say hello',
  'hello stackoverflow',
  'hello world',
  'foo bar bas'
);

$matches  = preg_grep ('/^hello (\w+)/i', $haystack);

print_r ($matches);

output

Array
(
    [1] => hello stackoverflow
    [2] => hello world
)

Documentation

• PHP: preg_grep - Manual

How to extract only the matching text from array elements?

array_reduce with preg_match can solve this issue in clean manner; see the snippet below.

$haystack = array (
  'say hello',
  'hello stackoverflow',
  'hello world',
  'foo bar bas'
);

function _matcher (str) {
  if (preg_match ('/^hello (\w+)/i', matches))
    matches[1];

  return $m;
}

// N O T E :
// ------------------------------------------------------------------------------
// you could specify '_matcher' as an anonymous function directly to
// array_reduce though that kind of decreases readability and is therefore
// not recommended, but it is possible.

$matches = array_reduce ($haystack, '_matcher', array ());

print_r ($matches);

output

Array
(
    [0] => stackoverflow
    [1] => world
)

Documentation

• PHP: array_reduce - Manual
• PHP: preg_match - Manual

Using array_reduce seems tedious, is there another way?

Yes, and this one is actually cleaner though it doesn't involve using any pre-existing array_* or preg_* function.

Wrap it in a function if you are going to use this method more than once.

$matches = array ();

foreach ($haystack as $str) 
  if (preg_match ('/^hello (\w+)/i', m))
    $matches[] = $m[1];

Documentation

• PHP: preg_match - Manual

First of all, if you literally are only doing dozens every minute, then I wouldn't worry terribly about the performance in this case. These matches are pretty quick, and I don't think you're going to have a performance problem by iterating through your patterns array and calling preg_match separately like this:

$matches = false;
foreach ($pattern_array as $pattern)
{
  if (preg_match($pattern, $page))
  {
    $matches = true;
  } 
}

You can indeed combine all the patterns into one using the or operator like some people are suggesting, but don't just slap them together with a |. This will break badly if any of your patterns contain the or operator.

I would recommend at least grouping your patterns using parenthesis like:

foreach ($patterns as $pattern)
{
  $grouped_patterns[] = "(" . $pattern . ")";
}
$master_pattern = implode($grouped_patterns, "|");

But... I'm not really sure if this ends up being faster. Something has to loop through them, whether it's the preg_match or PHP. If I had to guess I'd guess that individual matches would be close to as fast and easier to read and maintain.

Lastly, if performance is what you're looking for here, I think the most important thing to do is pull out the non regex matches into a simple "string contains" check. I would imagine that some of your checks must be simple string checks like looking to see if "This Site is Closed" is on the page.

So doing this:

foreach ($strings_to_match as $string_to_match)
{
  if (strpos($page, $string_to_match) !== false))
  {
    // etc.
    break;
  }
}
foreach ($pattern_array as $pattern)
{
  if (preg_match($pattern, $page))
  {
    // etc.
    break;
  } 
}

and avoiding as many preg_match() as possible is probably going to be your best gain. strpos() is a lot faster than preg_match().

How about this:

$badWords = array('one', 'two', 'three');
$stringToCheck = 'some stringy thing';
// $stringToCheck = 'one stringy thing';

$noBadWordsFound = true;
foreach ($badWords as $badWord) {
  if (preg_match("/\b$badWord\b/", $stringToCheck)) {
    $noBadWordsFound = false;
    break;
  }
}
if ($noBadWordsFound) { ... } else { ... }