Convert spaces between PRE tags, via DOM parser

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Regex was my original idea as a solution, although it soon became apparent a DOM parser would be more appropriate... I\'d like to convert spaces to b

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爱一瞬间的悲伤

2021-01-15 22:24
This is somewhat tricky when you want to insert   Entities without DOM converting the ampersand to & entities because Entities are nodes and spaces are just character data. Here is how to do it:
```
$dom = new DOMDocument;
$dom->loadHtml($html);
$xp = new DOMXPath($dom);
foreach ($xp->query('//text()[ancestor::pre]') as $textNode)
{
    $remaining = $textNode;
    while (($nextSpace = strpos($remaining->wholeText, ' ')) !== FALSE) {
        $remaining = $remaining->splitText($nextSpace);
        $remaining->nodeValue = substr($remaining->nodeValue, 1);
        $remaining->parentNode->insertBefore(
            $dom->createEntityReference('nbsp'),
            $remaining
        );
    }
}
```
Fetching all the pre elements and working with their nodeValues doesnt work here because the nodeValue attribute would contain the combined DOMText values of all the children, e.g. it would include the nodeValue of the span childs. Setting the nodeValue on the pre element would delete those.

So instead of fetching the pre nodes, we fetch all the DOMText nodes that have a pre element parent somewhere up on their axis:
```
DOMElement pre
    DOMText "abc 123"         <-- picking this
    DOMElement span
       DOMText "abc 123"      <-- and this one
DOMElement
    DOMText "123 123"         <-- and this one
```
We then go through each of those DOMText nodes and split them into separate DOMText nodes at each space. We remove the space and insert a nbsp Entity node before the split node, so in the end you get a tree like
```
DOMElement pre
    DOMText "abc"
    DOMEntity nbsp
    DOMText "123"
    DOMElement span
       DOMText "abc"
       DOMEntity nbsp
       DOMText "123"
DOMElement
    DOMText "123"
    DOMEntity nbsp
    DOMText "123"
```
Because we only worked with the DOMText nodes, any DOMElements are left untouched and so it will preserve the span elements inside the pre element.

Caveat:

Your snippet is not valid because it doesnt have a root element. When using loadHTML, libxml will add any missing structure to the DOM, which means you will get your snippet including a DOCTYPE, html and body tag back.

If you want the original snippet back, you'd have to getElementsByTagName the body node and fetch all the children to get the innerHTML. Unfortunately, there is no innerHTML function or property in PHP's DOM implementation, so we have to do that manually:
```
$innerHtml = '';
foreach ($dom->getElementsByTagName('body')->item(0)->childNodes as $child) {
    $tmp_doc = new DOMDocument();
    $tmp_doc->appendChild($tmp_doc->importNode($child,true));
    $innerHtml .= $tmp_doc->saveHTML();
}
echo $innerHtml;
```
Also see
- How to get innerHTML of DOMNode?
- DOMDocument in php
- https://stackoverflow.com/search?q=user%3A208809+dom
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时光说笑

2021-01-15 22:43

I see the short coming of my previous answer. Here is a workaround to preserve tags inside the <pre> tag:

<?php
$test = file_get_contents('input.html');
$dom = new DOMDocument('1.0');
$dom->loadHTML($test);
$xpath = new DOMXpath($dom);
$pre = $xpath->query('//pre//text()');
// manipulate nodes of type XML_TEXT_NODE
foreach($pre as $e) {
    $e->nodeValue = str_replace(' ', '__REPLACEMELATER__', $e->nodeValue);
    // when you attempt to write &nbsp; in a dom node
    // the & will be converted to &amp; :(
}
$temp = $dom->saveHTML();
$temp = str_replace('<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">', '', $temp);
$temp = str_replace('<html>', '', $temp);
$temp = str_replace('<body>', '', $temp);
$temp = str_replace('</body>', '', $temp);
$temp = str_replace('</html>', '', $temp);
$temp = str_replace('__REPLACEMELATER__', '&nbsp;', $temp);
echo $temp;
?>

Input

<p>paragraph 1 remains untouched</p>
<pre>preformatted 1</pre>
<div>
    <pre>preformatted 2</pre>
</div>
<div>
    <pre>preformatted 3 <span class="foo">span text</span> preformatted 3</pre>
</div>
<div>
    <pre>preformatted 4 <span class="foo">span <b class="bla">bold test</b> text</span> preformatted 3</pre>
</div>

Output

<p>paragraph 1 remains untouched</p>
<pre>preformatted&nbsp;1</pre>
<div>
    <pre>preformatted&nbsp;2</pre>
</div>
<div>
    <pre>preformatted&nbsp;3&nbsp;<span class="foo">span&nbsp;text</span>&nbsp;preformatted&nbsp;3</pre>
</div>
<div>
    <pre>preformatted&nbsp;4&nbsp;<span class="foo">span&nbsp;<b class="bla">bold&nbsp;test</b>&nbsp;text</span>&nbsp;preformatted&nbsp;3</pre>
</div>

Note #1

DOMDocument::saveHTML() method in PHP >= 5.3.6 allows you to specify the node to output. Otherwise you can use str_replace() or preg_replace() to elimitate doctype, html and body tags.

Note #2

This trick seems to work and results in one less line of code but I am not sure if it is guaranteed to work:

$e->nodeValue = utf8_encode(str_replace(' ', "\xA0", $e->nodeValue));
// dom library will attempt to convert 0xA0 to &nbsp;
// nodeValue expects utf-8 encoded data but 0xA0 is not valid in this encoding
// hence replaced string must be utf-8 encoded

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