How to balance tags with PHP

Question

In the string below, I want to replace <!--more--> with some text, FOOBAR, then truncate the string.

<p>The quick <a href="/">brown</a> fox jumps <!--more-->
over the <a href="/">lazy</a> dog.</p>

I've got to this point:

<p>The quick <a href="/">brown</a> fox jumps FOOBAR

... but as you can see, the <p> tag is not closed. Any ideas on how I could consistently balance the tags? I am pretty new to PHP.

The array I am working with looks like this:

array(2) {
  [0]=>
  string(50) "<p>The quick <a href="/">brown</a> fox jumps "
  [1]=>
  string(45) " over the <a href="/">lazy</a> dog.</p>"
}

Answer 1

As you state the problem, it's as easy as this:

str_replace('<!--more-->', 'FOOBAR', $original_text);

Perhaps if you update your question to explain what has an array to do with the whole problem will aid in interpreting the right question - (is the string <!--more--> supposed to be in the array?)

Answer 2

If possible, I would suggest parsing the HTML into a DOM and dealing with it that way, walking through text nodes until you find that string, then truncating the text node and deleting any further child nodes after that one (leaving the parent intact). Then re-serialize the DOM to HTML.

Answer 3

You would have to find all tags opened, but not closed, before the placeholder text. Insert the new text like you do now, and then close the tags afterwards.

Here is a sloppy example. I think this code will work with all valid HTML, but I'm not positive. And it will certainly accept invalid markup. but anyway:

$h = '<p>The quick <a href="/">brown</a> fox jumps <!--more-->
over the <a href="/">lazy</a> dog.</p>';

$parts = explode("<!--more-->", $h, 2);
$front = $parts[0];

/* Find all opened tags in the front string */
$tags = array();
preg_match_all("|<([a-z][\w]*)(?: +\w*=\"[\\w/%&=]+\")*>|i", $front, $tags, PREG_OFFSET_CAPTURE);
array_shift($tags); /* get rid of the complete match from preg_match_all */

/* Check if the opened arrays have been closed in the front string */
$unclosed = array();
foreach($tags as $t) {
    list($tag, $pos) = $t[0];
    if(strpos($front, "</".$tag, $pos) == false) {
     $unclosed[] = $tag;
    }
}    

/* Print the start, the replacement, and then close any open tags. */
echo $front;
echo "FOOBAR";
foreach($unclosed as $tag) {
    echo "</".$tag.">";
}

Outputs

<p>The quick <a href="/">brown</a> fox jumps FOOBAR</p>

Answer 4

I haven't fully tested this yet, but it works for your example at least. Assumes well-formed XML.

<?php
$reader = new XMLReader;
$writer = new XMLWriter;

// load the XML string into the XMLReader
$reader->xml('<p>The quick <a href="/">brown</a> fox jumps <!--more--> over the <a href="/">lazy</a> dog.</p>');
// write the new XML to memory
$writer->openMemory();
$done = false;

// XMLReader::read() moves the current read location to the next node
while ( !$done && $reader->read()) {
    // choose action based on the node type
    switch ($reader->nodeType) {
        case XMLReader::ELEMENT:
            // read an element, so write it back to the output
            $writer->startElement($reader->name);
            if ($reader->hasAttributes) {
                // loop through all attributes and write them
                while($reader->moveToNextAttribute()) {
                    $writer->writeAttribute($reader->name, $reader->value);
                }
                // move back to the beginning of the element
                $reader->moveToElement();
            }
            // if the tag is empty, close it now
            if ($reader->isEmptyElement) {
                $writer->endElement();
            }
            break;
        case XMLReader::END_ELEMENT:
            $writer->endElement();
            break;
        case XMLReader::TEXT:
            $writer->text($reader->value);
            break;
        case XMLReader::COMMENT:
            // you  can change this to be more flexible if you need
            // e.g. preg_match, trim, etc.
            if (trim($reader->value) == 'more') {

                // write whatever you want in here. If you have xml text
                // you want to write verbatim, use writeRaw() instead of text()
                $writer->text('FOOBAR');

                // this is where the magic happens -- endDocument closes
                // any remaining open tags
                $writer->endDocument();
                // stop the loop (could use "break 2", but that gets confusing
                $done = true;
            }
            break;
    }
}
echo $writer->outputMemory();