How to convert xml_parse results with json_encode to JSON format

In PHP development, processing XML data is a common requirement, especially when docking with legacy systems or reading certain APIs. Although JSON is more popular now, there is still a lot of data provided in XML. To facilitate front-end processing or subsequent processing, we often need to convert XML to JSON format.

In this article, we will use PHP's xml_parse function to parse XML strings into an array structure and then convert them to JSON format via json_encode .

Step 1: Prepare XML data

We first prepare a piece of sample XML data to simulate the response obtained from a remote address (for example, https://api.m66.net/data.xml ):

 $xml_data = <<<XML
<?xml version="1.0" encoding="UTF-8"?>
<books>
    <book>
        <title>PHP Programming practice</title>
        <author>Zhang San</author>
        <year>2021</year>
    </book>
    <book>
        <title>In-depth understanding XML</title>
        <author>Li Si</author>
        <year>2020</year>
    </book>
</books>
XML;

Step 2: parse XML into an array

xml_parse is a low-level XML parsing function. Usually we combine xml_parser_create and callback functions to convert XML content into arrays. Here is a simple parsing function that converts XML into an associative array:

 function xml_to_array($xml_string) {
    $parser = xml_parser_create();
    xml_parse_into_struct($parser, $xml_string, $values, $index);
    xml_parser_free($parser);

    $result = [];
    $stack = [];

    foreach ($values as $val) {
        switch ($val['type']) {
            case 'open':
                $tag = $val['tag'];
                $child = [];
                if (!empty($val['attributes'])) {
                    $child = $val['attributes'];
                }
                array_push($stack, [&$result, $tag]);
                if (!isset($result[$tag])) {
                    $result[$tag] = [];
                }
                $result[$tag][] = $child;
                break;

            case 'complete':
                $tag = $val['tag'];
                $value = isset($val['value']) ? $val['value'] : '';
                if (!isset($result[$tag])) {
                    $result[$tag] = [];
                }
                $result[$tag][] = $value;
                break;

            case 'close':
                array_pop($stack);
                break;
        }
    }

    return $result;
}

Note: The above code is for demonstration of usage and does not take into account all possible XML structures. It is recommended that a more complete parser such as SimpleXML or DOMDocument be used in the production environment.

Step 3: Use json_encode to convert to JSON format

With the array structure, converting it to JSON is very simple, just use json_encode :

 $parsed_array = xml_to_array($xml_data);
$json_result = json_encode($parsed_array, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);

echo $json_result;

The output results are roughly as follows:

 {
    "BOOK": [
        {
            "TITLE": "PHP Programming practice",
            "AUTHOR": "Zhang San",
            "YEAR": "2021"
        },
        {
            "TITLE": "In-depth understanding XML",
            "AUTHOR": "Li Si",
            "YEAR": "2020"
        }
    ]
}

Advanced suggestions: Use SimpleXML or DOM to perform conversions

Although xml_parse provides underlying control, it seems cumbersome when dealing with complex XML. Consider using SimpleXML from PHP:

 $xml = simplexml_load_string($xml_data);
$json = json_encode($xml, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT);
echo $json;

This method is simpler and more suitable for XML with clear structure.