Alternative to php preg_match to pull data from an external website?

Question

I want to extrat the content of a specific div in an external webpage, the div looks like this:

<dt>Win rate</dt><dd><div>50%</div></dd>

My target is the "50%". I'm actually using this php code to extract the content:

function getvalue($parameter,$content){
    preg_match($parameter, $content, $match);
    return $match[1];
    };
$parameter = '#<dt>Score</dt><dd><div>(.*)</div></dd>#';
$content = file_get_contents('https://somewebpage.com');

Everything works fine, the problem is that this method is taking too much time, especially if I've to use it several times with diferents $content.

I would like to know if there's a better (faster, simplier, etc.) way to acomplish the same function? Thx!

Answer 1

There are basically three main things you can do to improve the speed of your code:

Off load the external page load to another time (i.e. use cron)

On a linux based server I would know what to suggest but seeing as you use Windows I'm not sure what the equivalent would be, but Cron for linux allows you to fire off scripts at certain schedule time offsets - in the background - so not using a browser. Basically I would recommend that you create a script who's sole purpose is to go and fetch the website pages at a particular time offset (depending on how frequently you need to update your data) and then write those webpages to files on your local system.

$listOfSites = array(
  'http://www.something.com/page.htm',
  'http://www.something-else.co.uk/index.php',
);

$dirToContainSites = getcwd() . '/sites';

foreach ( $listOfSites as $site ) {
  $content = file_get_contents( $site );

  /// i've just simply converted the URL into a filename here, there are
  /// better ways of handling this, but this at least keeps things simple.
  /// the following just converts any non letter or non number into an
  /// underscore... so, http___www_something_com_page_htm
  $file_name = preg_replace('/[^a-z0-9]/i','_', $site);

  file_put_contents( $dirToContainSites . '/' . $file_name, $content );
}

Once you've created this script, you then need to set the server up to execute it as regularly as you need. Then you can modify your front-end script that displays the stats to read from local files, this would give a significant speed increase.

You can find out how to read files from a directory here:

http://uk.php.net/manual/en/function.dir.php

Or the simpler method (but prone to possible problems) is just to re-step your array of sites, convert the URLs to file names using the preg_replace above, and then check for the file's existence in the folder.

Cache the result of calculating your statistics

It's quite likely this being a stats page that you'll want to visit it quite frequently (not as frequent as a public page, but still). If the same page is visited more often than the cron-based script is executed then there is no reason to do all the calculation again. So basically all you have to do to cache your output is do something similar to the following:

$cachedVersion = getcwd() . '/cached/stats.html';

/// check to see if there is a cached version of this page
if ( file_exists($cachedVersion) ) {
  /// if so, load it and echo it to the browser
  echo file_get_contents($cachedVersion);
}
else {
  /// start output buffering so we can catch what we send to the browser
  ob_start();

  /// DO YOUR STATS CALCULATION HERE AND ECHO IT TO THE BROWSER LIKE NORMAL

  /// end output buffering and grab the contents so we now have a string
  /// of the page we've just generated
  $content = ob_get_contents(); ob_end_clean();

  /// write the content to the cached file for next time
  file_put_contents($cachedVersion, $content);

  echo $content;
}

Once you start caching things you need to be aware of when you should delete or clear your cache - otherwise if you don't your stats output will never change. With regards to this situation, the best time to clear your cache is at the point you go and fetch the external web pages again. So you should add this line to the bottom of your "cron" script.

$cachedVersion = getcwd() . '/cached/stats.html';

unlink( $cachedVersion ); /// will delete the file

There are other speed improvements you could make to the caching system (you could even record the modified times of the external webpages and load only when they have been updated) but I've tried to keep things easy to explain.

Don't use a HTML Parser for this situation

Scanning a HTML file for one particular unique value does not require the use of a fully-blown or even lightweight HTML Parser. Using RegExp incorrectly seems to be one of those things that lots of start-up programmers fall into, and is a question that is always asked. This has led to lots of automatic knee-jerk reactions from more experience coders to automatically adhere to the following logic:

if ( $askedAboutUsingRegExpForHTML ) {
  $automatically->orderTheSillyPersonToUse( $HTMLParser );
} else {
  $soundAdvice = $think->about( $theSituation );
  print $soundAdvice;
}

HTMLParsers should be used when the target within the markup is not so unique, or your pattern to match relies on such flimsy rules that it'll break the second an extra tag or character occurs. They should be used to make your code more reliable, not if you want to speed things up. Even parsers that do not build a tree of all the elements will still be using some form of string searching or regular expression notation, so unless the library-code you are using has been compiled in an extremely optimised manner, it will not beat well coded strpos/preg_match logic.

Considering I have not seen the HTML you are hoping to parse, I could be way off, but from what I've seen of your snippet it should be quite easy to find the value using a combination of strpos and preg_match. Obviously if your HTML is more complex and might have random multiple occurances of <dt>Win rate</dt><dd><div>50%</div></dd> it will cause problems - but even so - a HTMLParser would still have the same problem.

$offset = 0;

/// loop through the occurances of 'Win rate'
while ( ($p = stripos ($html, 'win rate', $offset)) !== FALSE ) {

  /// grab out a snippet of the surrounding HTML to speed up the RegExp
  $snippet = substr($html, $p, $p + 50 ); 

  /// I've extended your RegExp to try and account for 'white space' that could
  /// occur around the elements. The following wont take in to account any random
  /// attributes that may appear, so if you find some pages aren't working - echo
  /// out the $snippet var using something like "echo '<xmp>'.$snippet.'</xmp>';"
  /// and that should show you what is appearing that is breaking the RegExp.

  if ( preg_match('#^win\s+rate\s*</dt>\s*<dd>\s*<div>\s*([0-9]+%)\s*<#i', $snippet, $regs) ) {
    /// once you are here your % value will be in $regs[1];
    break; /// exit the while loop as we have found our 'Win rate'
  }

  /// reset our offset for the next loop
  $offset = $p;
}

Gotchas to be aware of

If you are new to PHP, as you state in a comment above, then the above may seem rather complicated - which it is. What you are trying to do is quite complex, especially if you want to do it optimally and fast. However, if you follow throught the code I've given and research any bits that you aren't sure of / haven't heard of (php.net is your friend), it should give you a better understanding of a good way to achieve what you are doing.

Guessing ahead however, here are some of the problems you might face with the above:

• File Permission errors - in order to be able to read and write files to and from the local operating system you will need to have the correct permissions to do so. If you find you can not write files to a particular directory it might be that the host you are using wont allow you to do so. If this is the case you can either contact them to ask about how to get write permission to a folder, or if that isn't possible you can easily change the code above to use a database instead.

• I can't see my content - when using output buffering all the echo and print commands do not get sent to the browser, they instead get saved up in memory. PHP should automatically output all the stored content when the script exits, but if you use a command like ob_end_clean() this actually wipes the 'buffer' so all the content is erased. This can lead to confusing situations when you know you are echoing something.. but it just isn't appearing.

(Mini Disclaimer :) I've typed all the above manually so you may find there are PHP errors, if so, and they are baffling, just write them back here and StackOverflow can help you out)

Answer 2

You may use DOMDocument::loadHTML and navigate your way to the given node.

$content = file_get_contents('https://somewebpage.com');
$doc = new DOMDocument();
$doc->loadHTML($content);

Now to get to the desired node, you may use method DOMDocument::getElementsByTagName, e.g.

$dds = $doc->getElementsByTagName('dd');
foreach($dds as $dd) {
  // process each <dd> element here, extract inner div and its inner html...
}

Edit: I see a point @pebbl has made about DomDocument being slower. Indeed it is, however, parsing HTML with preg_match is a call for trouble; In that case, I'd also recommend looking at event-driven SAX XML parser. It is much more lightweight, faster and less memory intensive as it does not build a tree. You may take a look at XML_HTMLSax for such a parser.

Answer 3

Instead of trying to not use preg_match why not just trim your document contents down in size? for example, you could dump everything before <body and everything after </body>. then preg_match will be searching less content already.

Also, you could try to do each one of these processes as a pseudo separate thread, so that way they aren't happening one at a time.