PHP preg_match problem

Question

Hi guys i'm having a problem, I have the following code:

<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=9,0,115,0" width="320" height="240">
<param name="movie" value="http://www.domain.com" />
<param name="quality" value="high" />
<param name="wmode" value="opaque" />
<param name="allowfullscreen" value="true" />
<param name="allowscriptaccess" value="always" />
<param name="FlashVars" value="file=http://www.domain.com/file.flv&amp;screenfile=http://domain.com/file.jpg&amp;dom=domain.com" />
<embed src="http://www.domain.com" width="320" height="240" bgcolor="#000000" type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer" allowfullscreen="true" flashvars="file=http://domain.com/file.flv&amp;screenfile=http://domain.com/file.jpg&amp;dom=domain.com" />
</object>

I need to get the value after screenfile= for example this one: http://domain.com/file.jpg ,but I have no idea how can I do that, and I will also need to replace the width and height propertis.

Thanks, any help is more then welcome!

Answer 1

Use /screenfile=([^&]+)/ to find the value of screenfile. $1 will contain the desired value. Parsing html with regex is not a good idea though.

To change the width:

  replace `/\bwidth="\d+"\b/` with width="423"

To change the height:

  replace `/\bheight="\d+"\b/` with height="565"

Answer 2

This is a common question on SO and the answer is always the same: regular expressions are a poor choice for parsing or processing HTML or XML. There are many ways they can break down. PHP comes with at least three built-in HTML parsers that will be far more robust.

Take a look at Parse HTML With PHP And DOM and use something like:

$html = new DomDocument;
$html->loadHTML($source); 
$html->preserveWhiteSpace = false; 
$params = $html->getElementsByTagName('param');
foreach ($params as $param) {
  if ($param->getAttribute('name') == 'FlashVars') {
    $params = decode_query_string($param->getAttribute('value'));
    $screen_file = $params['screenfile'];
  }
}
$embeds = $html->getElementsByTagName('embed');
$embed = $embed[0];
$embed->setAttribute('height', 300);
$embed->setAttribute('width', 400);
$raw_html = $html->saveHTML();

function decode_query_string($url) {
  $parts = parse_url($url);
  $query_string = $parts['query'];
  $vars = explode('&', $query_string);
  $ret = array();
  foreach ($vars as $var) {
    list($key, $value) = explode('=', $var, 2);
    $ret[urldecode($key)][] = urldecode($value);
  }
  return $ret;
}

Answer 3

Along the lines of:

$html = '<your HTML here>';

$dom = new DOMDocument;
$dom->loadHTML($html);

$xpath  = new DOMXPath($dom);
$result = $xpath->query('//object/param[@name = "FlashVars"][1]/@value');

foreach ($result as $node) {  // there should only be one
  preg_match(/screnfile=([^&]+)/, $node->nodeValue, $matches);
  print $matches[1];
}

Untested, but you get the idea. I would avoid using regex to parse HTML wherever possible, though in this case using regex alone could work (but since sample code and reality tend to diverge, I still recommend a parser based approach).