使用PHP从XML中具有相同父级的另一个子级的值中获取子级的值

Question

I have the following XML document:

<response>
    <message>
        <badgeid>13</badgeid>
        <level>4672</level>
        <completion_time>1518626787</completion_time>
        <xp>4922</xp>
        <scarcity>9717</scarcity>
    </message>
    <message>
        <badgeid>25</badgeid>
        <level>1</level>
        <completion_time>1480166791</completion_time>
        <xp>25</xp>
        <scarcity>3761041</scarcity>
    </message>
    <message>
        <badgeid>21</badgeid>
        <level>1</level>
        <completion_time>1467581153</completion_time>
        <xp>100</xp>
        <scarcity>16650345</scarcity>
    </message>
</response>

I am trying to create a program using PHP that returns the "scarcity" of a certain "badgeid" (that is always unique).

So my question is: How do I get the value of <scarcity></scarcity> when the only input I receive from the user is a unique badgeid ? In general words: How do I get the value of a child from the value of another child with the same parent?

Answer 1

You could also use an xpath expression and use the $badgeid as a parameter:

$expression = "/response/message[./badgeid='$badgeid']";

Then you could for example use SimpleXMLElement or DOMDocument .

$data = <<<DATA
<response>
    <message>
        <badgeid>13</badgeid>
        <level>4672</level>
        <completion_time>1518626787</completion_time>
        <xp>4922</xp>
        <scarcity>9717</scarcity>
    </message>
    <message>
        <badgeid>25</badgeid>
        <level>1</level>
        <completion_time>1480166791</completion_time>
        <xp>25</xp>
        <scarcity>3761041</scarcity>
    </message>
    <message>
        <badgeid>21</badgeid>
        <level>1</level>
        <completion_time>1467581153</completion_time>
        <xp>100</xp>
        <scarcity>16650345</scarcity>
    </message>
</response>
DATA;

$badgeid = 25;
$xml = simplexml_load_string($data);
$expression = "/response/message[./badgeid='$badgeid']";
$items = $xml->xpath($expression);

if (count($items) === 1) {
    echo $items[0]->scarcity;
}

$doc = new DOMDocument();
$doc->loadXML($data);
$xpath = new DOMXpath($doc);
$res = $xpath->query($expression);

if ($res->length === 1) {
    echo $res->item(0)->getElementsByTagName("scarcity")->item(0)->nodeValue;
}

Demo

Answer 2

You could use simplexml_load_string() for an XML string, or simplexml_load_file() if it is a XML file. Then you could iterate over $xml->message and check if $message->badgeid is the item you want :

$xmlstr = '<response>
    <message>
        <badgeid>13</badgeid>
        <level>4672</level>
        <completion_time>1518626787</completion_time>
        <xp>4922</xp>
        <scarcity>9717</scarcity>
    </message>
    <message>
        <badgeid>25</badgeid>
        <level>1</level>
        <completion_time>1480166791</completion_time>
        <xp>25</xp>
        <scarcity>3761041</scarcity>
    </message>
    <message>
        <badgeid>21</badgeid>
        <level>1</level>
        <completion_time>1467581153</completion_time>
        <xp>100</xp>
        <scarcity>16650345</scarcity>
    </message>
</response>';

$badgeid = 21 ; // The value you want to search
$xml = simplexml_load_string($xmlstr);
$scarcity = null ;
foreach ($xml->message as $message) {
    if ((string)$message->badgeid == $badgeid) {
        $scarcity = (string)$message->scarcity ;
        break ;
    }
}

// use $scarcity if set.
if (isset($scarcity)) {
    // do stuff
    echo $scarcity ; // 16650345
}