Scott B Scott B - 2 months ago 4x
PHP Question

parse content for appearance of a keyword inside h1, h2 and h3 heading tags

Given a block of content, I'm looking to create a function in PHP to check for the existence of a keyword or keyword phrase inside an h1-h3 header tags...

For example, if the keyword was "Blue Violin" and the block of text was...

You don't see many blue violins. Most violins have a natural finish.
<h1>If you see a blue violin, its really a rarity</h1>

I'd like my function to return:

  • The keyword phrase does appear in an h1 tag

  • The keyword phrase does not appear in an h2 tag

  • The keyword phrase does not appear in an h2 tag


You can use DOM and the following XPath for this:

/html/body//h1[contains(.,'Blue Violin')]

This would match all h1 element inside the body element containing the phrase "Blue Violin" either directly or in a subnode. If it should only occur in the direct TextNode, change the . to text(). The results are returned in a DOMNodeList.

Since you only want to know if the phrase appears, you can use the following code:

$dom = new DOMDocument;
$xPath = new DOMXPath($dom);
echo $xPath->evaluate('count(/html/body//h1[contains(.,"Blue Violin")])');

which will return the number of nodes matching this XPath. If your markup is not valid XHTML, you will not be able to use loadXML. Use loadHTML or loadHTMLFile instead. In addition, the XPath will execute faster if you give it a direct path to the nodes. If you only have one h1, h2 and h3 anyway, substitute the //h1 with a direct path.

Note that contains is case-sensitive, so the above will not match anything due to the Mixed Case used in the search phrase. Unfortunately, DOM (or better the underlying libxml) does only support XPath 1.0. I am not sure if there is an XPath function to do a case-insensitive search, but as of PHP 5.3, you can also use PHP inside an XPath, e.g.

$dom = new DOMDocument;
$xpath = new DOMXPath($dom);
$xpath->registerNamespace("php", "");
echo $xpath->evaluate('count(/html/body//h1[contains(php:functionString("strtolower", .),"blue violin")])');

so in case you need to match Mixed Case phrases or words, you can lowercase all text in the searched nodes before checking it with contains or use any other PHP function you may find useful here.