PHP or Regex for unique matching ID's - php

Question

Here's some stuff stored in a database table:
<section id="earth">
<h2>Earth</h2>
<div class="MainDiv">
(article)
</div>
</section>
<section id="mars">
<h2>Mars</h2>
<div class="MainDiv">
(article)
</div>
</section>
All I want to do is modify the display so each section has a unique data-target and each div has a matching ID. (I gave the div's a class - MainDiv - to distinguish them from any nested divs they might contain.)
<section id="earth" data-target="a">
<h2>Earth</h2>
<div class="MainDiv" id="a">
<section id="mars" data-target="b">
<h2>Mars</h2>
<div class="MainDiv" id="b">
Ideally, I'd like to keep the data-targets and matching ID's simple - single, lower case letters would be perfect. Is there a PHP function that can do that? If not, do you know a regex script that would work?

Answer 1

No, as much as possible, don't work on regex for this task. This is what HTML parsers are for. There is already a class for PHP that does this, its DOMDocument.
First, just load up the class (this is built-in already), then you load the HTML markup, get all the elements you need (in this case, the section tags). After you got all the section tags, iterate on those found and add those data attributes you want for each of those (including the div tags), then you put it back together as string again. Here's some to get you started. Rough Example:
$i = 1; // initialize counter
// initialize DOMDocument
$dom = new DOMDocument;
#$dom->loadHTML($html); // load the markup
$sections = $dom->getElementsByTagName('section'); // get all section tags
if($sections->length > 0) { // if there are indeed section tags inside
// work on each section
foreach($sections as $section) { // for each section tag
$section->setAttribute('data-target', 'section' . $i); // set id for section tag
// get div inside each section
foreach($section->getElementsByTagName('div') as $div) {
if($div->getAttribute('class') == 'MainDiv') { // if this div has class maindiv
$div->setAttribute('id', 'div' . $i); // set id for div tag
}
}
$i++; // increment counter
}
}
// back to string again, get all contents inside body
$html = '';
foreach($dom->getElementsByTagName('body')->item(0)->childNodes as $child) {
$html .= $dom->saveHTML($child); // convert to string and append to the container
}
// output
echo $html;
Sample Output

Answer 2

I would do as #Barmar suggested. Doing a0,a1,a2, ..., This way we can have as many as we want and echo each <section> in PHP via loop. If we went from a,b,c,...,z what would be next? aa? And you will have to program that in. For each element I would use a simple for loop and use the index for each element. For example this:
class Planet
{
public $title;
public $name;
public $article;
function __construct($title, $name, $article) {
$this->name = $name;
$this->title = $title;
$this->article = $article;
}
}
$planets = array(
new Planet("earth", "Earth", "Hello World!"),
new Planet("mars", "Mars", "Hello World Again!")
);
for( $i = 0; $i < count($planets); $i++ ) {
$id = strtolower($planets[$i]->name);
$name = $planets[$i]->name;
$article = $planets[$i]->article;
echo <<<HERE
<section id="$id" data-target="a$i">
<h2>$name</h2>
<div class="MainDiv" id="a$i">
$article
</div>
</section>
HERE;
}
Would give the output:
<section id="earth" data-target="a0">
<h2>Earth</h2>
<div class="MainDiv" id="a0">
Hello World!
</div>
</section>
<section id="mars" data-target="a1">
<h2>Mars</h2>
<div class="MainDiv" id="a1">
Hello World Again!
</div>
</section>