检查孩子是否存在？ - SimpleXML（PHP）

Question

I have different XML files where I renamed for each XML file all individual tags, so that every XML file has the same tag name. That was easy because the function was customized for the XML file.

But instand of writing 7 new functions for each XML file now I want to check if a XML file has a specidifed child or not. Because if I want to say:

foreach ($items as $item) {
$node = dom_import_simplexml($item);
$title = $node->getElementsByTagName('title')->item(0)->textContent;
$price = $node->getElementsByTagName('price')->item(0)->textContent;
$url = $node->getElementsByTagName('url')->item(0)->textContent;
$publisher = $node->getElementsByTagName('publisher')->item(0)->textContent;
$category = $node->getElementsByTagName('category')->item(0)->textContent;
$platform = $node->getElementsByTagName('platform')->item(0)->textContent;
}

I get sometimes: PHP Notice: Trying to get property of non-object in ...

For example. Two different XML sheets. One contains publisher, category and platform, the other not:

XML 1:

<products>
  <product>
    <desc>This is a Test</desc>
    <price>11.69</price>
    <price_base>12.99</price_base>
    <publisher>Stackoverflow</publisher>
    <category>PHP</category>
    </packshot>
    <title>Check if child exists? - SimpleXML (PHP)</title>
    <url>http://stackoverflow.com/questions/ask</url>
  </product>
</products>

XML 2:

<products>
  <product>
   <image></image>
    <title>Questions</title>
    <price>23,90</price>
    <url>google.de/url>
    <platform>Stackoverflow</platform>
  </product>
</products>

You see, sometimes one XML file contains publisher, category and platform but sometimes not. But it could also be that not every node of a XML file contains all attributes like in the first!

So I need to check for every node of a XML file individual if the node is containing publisher, category or/and platform.

How can I do that with SimpleXML? I thought about switch case but at first I need to check which childs are contained in every node.

EDIT: Maybe I found a solution. Is that a solution or not?

if($node->getElementsByTagName('platform')->item(0)){
        echo $node->getElementsByTagName('platform')->item(0)->textContent . "
";
    }

Greetings and Thank You!

Answer 1

One way to rome... (working example)

$xml = "<products>
  <product>
    <desc>This is a Test</desc>
    <price>11.69</price>
    <price_base>12.99</price_base>
    <publisher>Stackoverflow</publisher>
    <category>PHP</category>
    <title>Check if child exists? - SimpleXML (PHP)</title>
    <url>http://stackoverflow.com/questions/ask</url>
  </product>
</products>";
$xml = simplexml_load_string($xml);
#set fields to look for
foreach(['desc','title','price','publisher','category','platform','image','whatever'] as $path){
       #get the first node
       $result = $xml->xpath("product/{$path}[1]");
       #validate and set
       $coll[$path] = $result?(string)$result[0]:null;  
       #if you need here a local variable do (2 x $)
       ${$path} = $coll[$path];
}
#here i do array_filter() to remove all NULL entries
print_r(array_filter($coll));
#if local variables needed do
extract($coll);#this creates $desc, $price

Note </packshot> is an invalid node, removed here.

xpath syntax https://www.w3schools.com/xmL/xpath_syntax.asp