How to use preg in php to add html properties - php

Question

I'm looking to write a script in php that scans an html document and adds new markup to a element based on what it finds. More specifically, I was it to scan the document and for every element it searches for the CSS markup "float: right/left" and if it locates it, it adds align="right/left" (based on what it finds).
Example:
<img alt="steve" src="../this/that" style="height: 12px; width: 14px; float: right"/>
becomes
<img alt="steve" src="../this/that" align="right" style="height: 12px; width: 14px; float: right"/>

Answer 1

$dom = new DOMDocument();
$dom->loadHTML($htmlstring);
$x = new DOMXPath($dom);
foreach($x->query("//img[contains(#style,'float: right']") as $node) $node->setAttribute('align','right');
foreach($x->query("//img[contains(#style,'float: left']") as $node) $node->setAttribute('align','left');
edit:
When there is no certainty of amount of space between 'float:' & 'right', there are several options:
Use the XPath 1.0: //img[starts-with(normalize-space(substring-after(#style,'float:')),'right')]
Just do a simple check for float like //img[contains(#style,'float:'], and check with $node->getAttribute() what actually comes afterwards.
Import preg_match into the equasion (which was just recently pointed out to me (thanks Gordon), but in this case is imho the least favorite solution):
.
$dom = new DOMDocument();
$dom->loadHTML($htmlstring);
$x = new DOMXPath($dom);
$x->registerNamespace("php", "http://php.net/xpath");
$x->registerPHPFunctions('preg_match');
foreach($x->query("//img[php:functionString('preg_match','/float\s*:\s*right/',#style)]") as $node) $node->setAttribute('align','right');

Answer 2

Please please, don't use a regexp to parse HTML.
Use simple_html_dom instead.
$dom = new simple_html_dom();
$dom->load($html);
foreach ($dom->find("[style=float: left],[style=float: right]") as $fragment)
{
if ($fragment[0]->style == 'float:left')
{
$fragment[0]->align='left';
$fragment[0]->style = '';
}
...
}
echo $dom;