If it contains html (note that this is a pretty robust solution):
$string = '<p>foo<b>bar</b></p>';
$keyword = 'foo';
$dom = new DomDocument();
$dom->loadHtml($string);
$xpath = new DomXpath($dom);
$elements = $xpath->query('//*[contains(.,"'.$keyword.'")]');
foreach ($elements as $element) {
foreach ($element->childNodes as $child) {
if (!$child instanceof DomText) continue;
$fragment = $dom->createDocumentFragment();
$text = $child->textContent;
$stubs = array();
while (($pos = stripos($text, $keyword)) !== false) {
$fragment->appendChild(new DomText(substr($text, 0, $pos)));
$word = substr($text, $pos, strlen($keyword));
$highlight = $dom->createElement('span');
$highlight->appendChild(new DomText($word));
$highlight->setAttribute('class', 'highlight');
$fragment->appendChild($highlight);
$text = substr($text, $pos + strlen($keyword));
}
if (!empty($text)) $fragment->appendChild(new DomText($text));
$element->replaceChild($fragment, $child);
}
}
$string = $dom->saveXml($dom->getElementsByTagName('body')->item(0)->firstChild);
Results in:
<p><span class="highlight">foo</span><b>bar</b></p>
And with:
$string = '<body><p>foobarbaz<b>bar</b></p></body>';
$keyword = 'bar';
You get (broken onto multiple lines for readability):
<p>foo
<span class="highlight">bar</span>
baz
<b>
<span class="highlight">bar</span>
</b>
</p>
Beware of non-dom solutions (like regex or str_replace) since highlighting something like "div" has a tendency of completely destroying your HTML... This will only ever "highlight" strings in the body, never inside of a tag...
Edit Since you want Google style results, here's one way of doing it:
function getKeywordStubs($string, array $keywords, $maxStubSize = 10) {
$dom = new DomDocument();
$dom->loadHtml($string);
$xpath = new DomXpath($dom);
$results = array();
$maxStubHalf = ceil($maxStubSize / 2);
foreach ($keywords as $keyword) {
$elements = $xpath->query('//*[contains(.,"'.$keyword.'")]');
$replace = '<span class="highlight">'.$keyword.'</span>';
foreach ($elements as $element) {
$stub = $element->textContent;
$regex = '#^.*?((\w*\W*){'.
$maxStubHalf.'})('.
preg_quote($keyword, '#').
')((\w*\W*){'.
$maxStubHalf.'}).*?$#ims';
preg_match($regex, $stub, $match);
var_dump($regex, $match);
$stub = preg_replace($regex, '\\1\\3\\4', $stub);
$stub = str_ireplace($keyword, $replace, $stub);
$results[] = $stub;
}
}
$results = array_unique($results);
return $results;
}
Ok, so what that does is return an array of matches with $maxStubSize words around it (namely up to half that number before, and half after)...
So, given a string:
<p>a whole
<b>bunch of</b> text
<a>here for</a>
us to foo bar baz replace out from this string
<b>bar</b>
</p>
Calling getKeywordStubs($string, array('bar', 'bunch')) will result in:
array(4) {
[0]=>
string(75) "here for us to foo <span class="highlight">bar</span> baz replace out from "
[3]=>
string(34) "<span class="highlight">bar</span>"
[4]=>
string(62) "a whole <span class="highlight">bunch</span> of text here for "
[7]=>
string(39) "<span class="highlight">bunch</span> of"
}
So, then you could build your result blurb by sorting the list by strlen and then picking the two longest matches... (assuming php 5.3+):
usort($results, function($str1, $str2) {
return strlen($str2) - strlen($str1);
});
$description = implode('...', array_slice($results, 0, 2));
Which results in:
here for us to foo <span class="highlight">bar</span> baz replace out...a whole <span class="highlight">bunch</span> of text here for
I hope that helps... (I do feel this is a bit... bloated... I'm sure there are better ways to do this, but here's one way)...
