How can I search a XML file using regular expressions in php - php

Question

I am curious if I can search an XML file for a certain tag with regular expressions. I can search the file if I use fopen('foo.xml'); but it will only allow me to search the content between the tags not the tags them self. My objective for this is I hope to create a function that will allow me to delete all the content between two tags for example between users which are in a xml file. He language that I am using is PHP.
Thanks in advance john.

Answer 1

You should use something like SimpleXMLto handle/edit XML files.
If you really insist on doing it by treating the SML file as a string you can do something like this (or you can use regex). But you should use an XML library.
// get your file as a string
$yourXML = file_get_contents($file) ;
$posStart = stripos($yourXML,'<users>') + strlen('<users>') ;
$posEnd = stripos($yourXML,'</users>') ;
$newXML = substr($yourXML,0,$posStart) . substr($yourXML,$posEnd) ;
// <users> is now empty
echo $newXML ;

Answer 2

DomDocument & XPath will make things very clean, direct and reliable.
You can use evaluate() or query() as they provide the same result.
// will seek out the matching tags regardless of their location.
Be aware that my solution is case-sensitive.
Code: (Demo)
$xml = <<<XML
<myXml>
<Person>
<firstName>pradeep</firstName>
<lastName>jain</lastName>
<address>
<doorNumber>287</doorNumber>
<street>2nd block</street>
<city>bangalore</city>
</address>
<phoneNums type="mobile">9980572765</phoneNums>
<phoneNums type="landline">080 42056434</phoneNums>
<phoneNums type="skype">123456</phoneNums>
</Person>
<Person>
<firstName>pradeep</firstName>
<lastName>jain</lastName>
<address>
<doorNumber>287</doorNumber>
<street>2nd block</street>
<city>bangalore</city>
</address>
<phoneNums type="mobile">1</phoneNums>
<phoneNums type="landline">2</phoneNums>
<phoneNums type="skype">3</phoneNums>
</Person>
</myXml>
XML;
$dom = new DOMDocument;
$dom->loadXML($xml); // <-- you'll need to import your file instead of a string as demo'ed here
$xpath = new DOMXPath($dom);
echo count($xpath->evaluate("//phoneNums")) , "\n"; // 6
echo count($xpath->evaluate("//street")) , "\n"; // 2
echo count($xpath->evaluate("//myXml")) , "\n"; // 1
echo count($xpath->evaluate("//Person")) , "\n"; // 2
echo count($xpath->evaluate("//person")) , "\n"; // 0 <-- case-sensitive

Answer 3

As a simple mock up of the various parts needed to do this in SimpleXML, there are a few concepts you need to know to get it to work.
The main one being XPath, which a sort of SQL for XML. Of course it has it's own notation and can be a little pedantic at times, but you can experiment with it on sites like https://codebeautify.org/Xpath-Tester.
$data = '<?xml version="1.0" encoding="UTF-8"?>
<Users>
<User id="123">
<Name>fred</Name>
<Extension>1234</Extension>
</User>
<User id="124">
<Name>bert</Name>
<Extension>1235</Extension>
</User>
<User id="125">
<Name>foo</Name>
<Extension>1236</Extension>
</User>
</Users>';
$userID = "123";
$users = simplexml_load_string($data);
// Find the user with the id attribute (use [0] as the call to xpath
// returns a list of matches and you only want the first one)
$userMatch = $users->xpath("//User[#id='{$userID}']")[0];
// Just output user id attribute and name
echo "id=".$userMatch['id'].",name=".$userMatch->Name.PHP_EOL;
echo "Removing user...".PHP_EOL;
// Remove the user - note the [0] is required here
unset($userMatch[0]);
// Print out the resulting XML after the removal
echo $users->asXML();
I've put comments through the code as how it works. The output is...
id=123,name=fred
Removing user...
<?xml version="1.0" encoding="UTF-8"?>
<Users>
<User id="124">
<Name>bert</Name>
<Extension>1235</Extension>
</User>
<User id="125">
<Name>foo</Name>
<Extension>1236</Extension>
</User>
</Users>