QueryList recursive collection: analysis of differences between expected results and actual results and solutions

When using QueryList for multi-level data crawling, developers often encounter situations where the document examples are inconsistent with the actual running results. This article will use a case to deeply analyze the root causes of the problem and provide effective solutions.

Problem description:

The goal is to extract title and list information from the HTML structure. The HTML structure is as follows:

<div id="demo">
    <ul>
<li>
          <h3>xxx</h3>
          <div class="list">
            <div class="item">item1</div>
            <div class="item">item2</div>
          </div>
        </li>
         <li>
          <h3>xxx2</h3>
          <div class="list">
            <div class="item">item12</div>
            <div class="item">item22</div>
          </div>
        </li>
    </ul>
</div>

Use QueryList code for data extraction:

 // ... (Code snippet is missing, cannot be fully analyzed) ...

The expected result is to extract each<li> Next<h3></h3> Title and item content. But the actual result is the merger of item content:

 <code>Array ( [0] => Array ( [title] => xxx [list] => Array ( [item] => item1item2 ) ) [1] => Array ( [title] => xxx2 [list] => Array ( [item] => item12item22 ) ) )</code>

Problem analysis:

The problem is that the inner QueryList object inherits range parameters of the outer QueryList object. range('') ??does not really reset the selector, causing it to still use the selector of outer range('#demo li') , resulting in item content merge. This may be due to a QueryList internal mechanism or other issues in the code. range('') ??does not always reset the range correctly and requires more in-depth analysis.

Solution:

To solve this problem, it is necessary to ensure that the inner QueryList object works independently of the outer object. Simple range('') ??may not work, we need a more reliable method. The following solutions can be tried:

<li> Use more precise selectors: Avoid using range() , use more precise CSS selectors directly in rules , for example:

 $data = querylist::html($html)
    ->rules([
        'title' => ['h3', 'text'],
        'list' => ['.list .item', 'text'] // Select all .item elements directly])
    ->range('#demo li')
    ->query(); // Note that query() is used directly here, and the recursive dump($data) of querydata() is no longer needed;

This method directly extracts the text content of all .item elements, avoiding the problems caused by recursion.

<li> Manual loop processing: Abandon the recursive function of QueryList and manually loop processing each<li> element:

 $lis = querylist::html($html)->find('#demo li');
$data = [];
foreach ($lis as $li) {
    $item = [];
    $item['title'] = querylist::html($li)->find('h3')->text();
    $items = querylist::html($li)->find('.list .item')->map(function($item){return $item->text();})->all();
    $item['list'] = $items;
    $data[] = $item;
}
dump($data);

This method is clearer and easier to understand and debug.

<li> In-depth examination of the QueryList source code and documentation: If the above method is invalid, you need to conduct in-depth research on the QueryList source code and documentation, find out the specific behavior and potential problems of range() method, and try other functions provided by QueryList to solve this problem. You may need to check the QueryList version and PHP version compatibility.

Which option to choose depends on the specific requirements and familiarity with QueryList. It is recommended to give priority to method 1, because it is simple and efficient. If Method 1 cannot meet the requirements, consider Method 2 again. Method 3 is the last choice and requires more in-depth programming knowledge. Remember to always check the official documentation and sample code of QueryList to ensure its features are used correctly.

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