How to search an XML file's content similar to a MySQL query?

I can read the input of a xml file in an array simply like this :

  <?php
  $doc = new DOMDocument();
  $doc->load( 'books.xml' );

  $books = $doc->getElementsByTagName( "book" );
  foreach( $books as $book )
  {
  $authors = $book->getElementsByTagName( "author" );
  $author = $authors->item(0)->nodeValue;

  $publishers = $book->getElementsByTagName( "publisher" );
  $publisher = $publishers->item(0)->nodeValue;

  $titles = $book->getElementsByTagName( "title" );
  $title = $titles->item(0)->nodeValue;

  echo "$title - $author - $publisher\n";
  }
  ?>

And lets the xml file to an example something like this :

  <books>
  <book>
  <aut开发者_JS百科hor>Jack Herrington</author>
  <title>PHP Hacks</title>
  <publisher>O'Reilly</publisher>
  </book>
  <book>
  <author>Jack Herrington</author>
  <title>Podcasting Hacks</title>
  <publisher>O'Reilly</publisher>
  </book>
  </books>

But If i want to match at a certain level lets say I want to FIND the number of matching elements like in mySql has LIKE or ==.

And return the result to an array or something

---

XPATH is what you are looking for I think.

For instance, all books published by O'Reilly:

<?php
$doc = new DOMDocument();
$doc->load( '/tmp/books.xml' );
$x = new DOMXPath($doc);
foreach($x->query('//book[publisher="O\'Reilly"]') as $book){
    echo $book->ownerDocument->saveXML($book);
}
//If you only want the count:
echo $x->evaluate('count(//book[publisher="O\'Reilly"])');

XPath is my opinion more easy to learn then SQL, but by no means a 'look at it for a couple of minutes and you're done', you'll really have to learn it if your needs are more complex then the bare basics.

---

If you parse your document using SimpleXML instead of DOMDocument, you can use xpath to find elements in your document. I don't know if this will match your needs exactly, but I have done some pretty complex, dynamic paths (queries) before:

http://php.net/manual/en/simplexmlelement.xpath.php