PHP 新 DOM 選擇器功能指南

DOMElement querySelector(string $selector)

$doc = new DOMDocument();
$doc->loadHTML('<div>



<p>This method returns the <strong>first element</strong> matching the provided CSS selector. If no element is found, it returns null.</p>

<h4>
  
  
  2. querySelectorAll()
</h4>

<p>The querySelectorAll() method allows you to select <strong>all elements</strong> matching the provided CSS selector. It returns a DOMNodeList object, which is a collection of DOM elements.</p>

<p><strong>Syntax</strong> :<br>
</p>

<pre class="brush:php;toolbar:false">DOMNodeList querySelectorAll(string $selector)

$doc = new DOMDocument();
$doc->loadHTML('<div>



<p>This method returns a DOMNodeList containing all elements matching the given CSS selector. If no elements are found, it returns an empty DOMNodeList.</p>

<h2>
  
  
  Key Benefits of the DOM Selector
</h2>

<p>CSS selector in PHP 8.4 brings several key advantages to developers, the new methods streamline DOM element selection, making your code cleaner, more flexible, and easier to maintain.</p>

<h3>
  
  
  1. Cleaner and More Intuitive Syntax
</h3>

<p>With the new DOM selector methods, you can now use the familiar CSS selector syntax, which is much more concise and readable. No longer do you need to write out complex loops to traverse the DOM just provide a selector, and PHP will handle the rest.</p>

<h3>
  
  
  2. Greater Flexibility
</h3>

<p>The ability to use CSS selectors means you can select elements based on attributes, pseudo-classes, and other criteria, making it easier to target specific elements in the DOM.</p>

<p>For example, you can use:</p>

<ul>
<li>.class</li>
<li>#id</li>
<li>div > p:first-child

$doc = new DOMDocument();
$doc->loadHTML('<div>



<p>This code selects the element with the>

<h3>
  
  
  By Class
</h3>

<p>The querySelectorAll('.class') method selects all elements with a given class, making it easy to manipulate groups of elements, like buttons or list items, in one go.<br>
</p>

<pre class="brush:php;toolbar:false">$doc = new DOMDocument();
$doc->loadHTML('<div>



<p>This code selects all elements with the class item and outputs their text content. It’s ideal for working with multiple elements that share the same class name.</p>

<h3>
  
  
  Nested Elements
</h3>

<p>The querySelectorAll('.parent > .child') method targets direct children of a specific parent, making it easier to work with nested structures like lists or tables.<br>


<pre class="brush:php;toolbar:false">$doc = new DOMDocument();
$doc->loadHTML('<ul>



<p>This code selects the <li> elements that are direct children of the .list class and outputs their text content. The > combinator ensures only immediate child elements are selected, making it useful for working with nested structures.

<h2>
  
  
  Example Web Scraper using Dom Selector
</h2>

<p>Here's an example PHP web scraper using the new DOM selector functionality introduced in PHP 8.4. This script extracts product data from the given product page:<br>
</p>

<pre class="brush:php;toolbar:false"><?php

// Load the HTML of the product page
$url = 'https://web-scraping.dev/product/1';
$html = file_get_contents($url);

// Create a new DOMDocument instance and load the HTML
$doc = new DOMDocument();
libxml_use_internal_errors(true); // Suppress warnings for malformed HTML
$doc->loadHTML($html);
libxml_clear_errors();

// Extract product data using querySelector and querySelectorAll
$product = [];

// Extract product title
$titleElement = $doc->querySelector('h1');
$product['title'] = $titleElement ? $titleElement->textContent : null;

// Extract product description
$descriptionElement = $doc->querySelector('.description');
$product['description'] = $descriptionElement ? $descriptionElement->textContent : null;

// Extract product price
$priceElement = $doc->querySelector('.price');
$product['price'] = $priceElement ? $priceElement->textContent : null;

// Extract product variants
$variantElements = $doc->querySelectorAll('.variants option');
$product['variants'] = [];
if ($variantElements) {
    foreach ($variantElements as $variant) {
        $product['variants'][] = $variant->textContent;
    }
}

// Extract product image URLs
$imageElements = $doc->querySelectorAll('.product-images img');
$product['images'] = [];
if ($imageElements) {
    foreach ($imageElements as $img) {
        $product['images'][] = $img->getAttribute('src');
    }
}

// Output the extracted product data
echo json_encode($product, JSON_PRETTY_PRINT);