creating preg_match using xpath in php

Question

I am trying to get the contents using XPATH in php.

<div class='post-body entry-content' id='post-body-37'>
<div style="text-align: left;">
<div style="text-align: center;">
Hi
</div></div></div>

I am using below php code to get the output.

 $dom = new DOMDocument;
 libxml_use_internal_errors(true);
 $dom->loadHTML($html);
 $xpath = new DOMXPath($dom);
 $xpath->registerPhpFunctions('preg_match');
 $regex = 'post-(content|[a-z]+)';
 $items = $xpath->query("div[ php:functionString('preg_match', '$regex', @class) > 0]");
 dd($items);

It returns output as below

DOMNodeList {#580 
+length: 0 
}

Shouldn't the regex be delimited? Try `$regex = '/post-(content|[a-z]+)/';` — hjpotter92, Oct 29 '15 at 08:32
sorry typo from my side.. I used $regex = '/post-(content|[a-z]+)/'; in code — karthick, Oct 29 '15 at 08:34
See [this demo](https://ideone.com/4JIWRt), you do not need regex. — Wiktor Stribiżew, Oct 29 '15 at 08:50
yeah.. But I am looking for class which starts with **post-** and contains **content*. As I mentioned in the above code, I am using above regex because some will have as
ans some will have as
. I need to parse both options. If you look at the first one, it contains two classes **post-body entry-content* and if you look at the second one, it contains only one class **post-conten**. I need to get through this also. — karthick, Oct 29 '15 at 08:52
Good, so you can use [`$xp->query('//div[starts-with(@class,"post-") and contains(@class, "content")]');`](https://ideone.com/l9r4fG). — Wiktor Stribiżew, Oct 29 '15 at 08:54
got it.. thanks.. but as a concern if i need to use regex how can i use??? — karthick, Oct 29 '15 at 08:57
@karthick: Thank you for a nice question, let's live and learn! — Wiktor Stribiżew, Oct 29 '15 at 09:31

Casimir et Hippolyte · Answer 1 · 2015-10-29T09:21:37.753

Here is a working version with the different advices you get in comments:

libxml_use_internal_errors(true);

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

$xpath = new DOMXPath($dom);
// you need to register the namespace "php" to make it available in the query
$xpath->registerNamespace("php", "http://php.net/xpath"); 
$xpath->registerPhpFunctions('preg_match');

// add delimiters to your pattern
$regex = '~post-(content|[a-z]+)~';

// search your node anywhere in the DOM tree with "//"
$items = $xpath->query("//div[php:functionString('preg_match', '$regex', @class)>0]");

var_dump($items);

Obviously, this kind of pattern is useless since you can get the same result with available XPATH string functions like contains.

does `>0` mean that if it matches `do something` and if not ignore it? — Motivated, Aug 19 '22 at 07:49

Wiktor Stribiżew · Accepted Answer · 2019-12-16T10:19:35.087

For a simple task like this - getting the div nodes with class attribute starting with post- and containing content, you should be using regular simple XPath queries:

$xp->query('//div[starts-with(@class,"post-") and contains(@class, "content")]');

Here, - //div - get all divs that... - starts-with(@class,"post-") - have "class" attribute starting with "post-" - and - and... - contains(@class, "content") - contain "content" substring in the class attribute value.

To use the php:functionString you need to register the php namespace (with $xpath->registerNamespace("php", "http://php.net/xpath");) and the PHP functions (to register them all use $xp->registerPHPFunctions();).

For complex scenrios, when you need to analyze the values even deeper, you may want to create and register your own functions:

function example($attr) {
    return preg_match('/post-(content|[a-z]+)/i', $attr) > 0;
}

and then inside XPath:

$divs = $xp->query("//div[php:functionString('example', @class)]");

Here, functionString passes the string contents of @class attribute to the example function, not the object (as would be the case with php:function).

See IDEONE demo:

function example($attr) {
    return preg_match('/post-(content|[a-z]+)/i', $attr) > 0;
}
$html = <<<HTML
<body>
<div class='post-body entry-content' id='post-body-37'>
<div style="text-align: left;">
<div style="text-align: center;">
Hi
</div></div></div>
</body>
HTML;
$dom = new DOMDocument;
$dom->loadHTML($html, LIBXML_HTML_NOIMPLIED|LIBXML_HTML_NODEFDTD);

$xp = new DOMXPath($dom);
$xp->registerNamespace("php", "http://php.net/xpath");
$xp->registerPHPFunctions('example');
$divs = $xp->query("//div[php:functionString('example', @class)]");
foreach ($divs as $div) {
    echo $div->nodeValue;    
}

See also a nice article about the using of PhpFunctions inside XPath in Using PHP Functions in XPath Expressions.

creating preg_match using xpath in php

2 Answers2