xpath找不到任何东西 - PHP

Question

Introduction

I have some codes in SQL. I go code by code in while loop in php and search these codes in XML feed.

Programm code

I have the following programm code

$x_search = $xml->xpath("//Item[@Sort='$sort']");
if(!$x_search){
    $x_Id = $x_search[0]->attributes()->Id;
    echo $sort." - ".$x_Id."<BR />";
}

Problem

It is possible, that some code is not in SQL. So I get this error message:

Undefined offset: 0 in

How to do something like if you find it in XML, $x_Id = $x_search[0]->attributes()->Id;?

I have tried already:

1. $x_search = $xml->xpath("//*[@Sort='$sort']");
2. if(!empty($x_search)){
3. if(isset($x_search)){

Example XML:

<?xml version="1.0" encoding="utf-8"?>
<Root>
  <Item Id="12860" IdP="-2147483648" Sort="0001KC" Name="Computers">
    <StoItem />
  </Item>
</Root>

Examples for $sort:

00004M
12860
12859
12859
12861
12861
12862
12862
12863
12863
12864

Thank you

Answer 1

SimpleXMLElement::xpath() always returns an array of SimpleXMLElement objects. The array is empty, if nothing is matched. The result can equal false, if the expression is invalid (programming error). So if (!empty($x_search)) ... or if ($x_search) ... can be used as condition to check the result. false is an empty value and an empty array equals false. Both conditions will only be true if the result from the expression is an array with at least a single element.

$xmlString = <<<'XML'
<?xml version="1.0" encoding="utf-8"?>
<Root>
  <Item Id="12860" IdP="-2147483648" Sort="0001KC" Name="Computers">
    <StoItem />
  </Item>
</Root>
XML;

$xml = new SimpleXmlElement($xmlString);
$sort = '0001KC';

$x_search = $xml->xpath("//Item[@Sort='$sort']");
if (!empty($x_search)) {
    $x_Id = $x_search[0]->attributes()->Id;
    echo $sort." - ".$x_Id."<BR />";
}

Output: https://eval.in/406640

0001KC - 12860<BR />

Most of your example values for $sort look like Id attribute values. The second one, is the Id attribute value in the example XML.

If you want to match the Id attribute, the Xpath expression would be:

//Item[@Id='$sort']

It is even possible to match both attributes:

//Item[@Id='$sort' or @Sort='$sort']