XML

XML:

• XML is Extended Markup Language.
• DTD or Document Type Definition gives information about structure and content of the particular XML.
• An entity is a named storage using like say head tag.
• An element usually has attributes and other texts.
• Finally, there is the content or value of the entity.

SimpleXML:

SimpleXML is a PHP 5 library that takes care of working with XML. Some methods are available after 5.1.3.

$library = new SimpleXMLElement($xmlstr);                   //Load XML from string.
$library = new SimpleXMLElement(library.xml, NULL, true);   //Load XML from file. True tells first parameter is a path to the file.

foreach ($library->book as $book)                           //Looping through many books is library. Children.
{
echo $book[isbn] . "n";                                     //Accessing an attribute.
echo $book->title . "n";                                    //Accessing a child.
}

foreach ($library->children() as $child => $valuechild)     //Get children of this element.
{
echo $child->getName()."=".$child;                          //Example a = this is a link.
echo   $child."=". $valuechild;                             //Example a = this is a link.           
foreach ($child->attributes() as $attr => $valueattr)       //Get attributes of this element.
{
echo $attr->getName()."=".$attr;                            //Example target = _blank.
echo   $attr."=". $valueattr;                               //Example target = _blank.
}
}

XPATH:

XPath or XML Path Language is a way to access and search XML Documents.

$results = $library->xpath(/library/book/title);        //Returns the XML Object under the XPath.

$newbook = $book->addChild(title, "Enders Game");       ///Adding a child. Third optional parameter is namespace.
$book->addAttribute(isbn, 0812550706);                  //Adding an attribute. Third optional parameter is namespace.

header(Content-type: text/xml);                         //Header for XML.
echo $library->asXML();                                 //Print XML.

//Remove the children of book[0]. You cannot remove an attribute of book. You can only set them to empty. For that to happen we will have to export to DOM and use a powerful functionality there.
$library->book[0] = NULL;               

$namespaces = $library->getDocNamespaces();             //Gets namespaces declared in the root element referenced. By passing true all namespaces declared recursively in children will be returned.
foreach ($namespaces as $key => $value)
{
echo "{$key} => {$value}";
}

$namespaces = $library->getNamespaces(true);            //Gets namespaces used (not declared) in the root element referenced. Passing True will return all namespaces used recursively in children will be returned.

DOM:

DOM is Document Object Model.

$dom = new DomDocument();

$dom->load(library.xml);                   //Load from file.
$dom->loadXML($xml);                       //Load from XMl string.

$dom->loadHTMLFile("librabry.html");       //Load from HTML file.
$dom->loadHTML($html);                     //Load from HTML string.

$dom->saveXML();                           //Save as XMl.
$dom->saveHTML();                          //Save as HTML.

$element = $dom->createElement("a", 'This is a link!'); //Creates an element.
$element = $dom->getAttribute("target");                //Returns value of attribute.
$element = $dom->hasAttribute("target");                //Checks to see if attribute exists. Returns TRUE or FALSE.
$element = $dom->setAttribute("target","_blank");       //Adds new attribute. Returns sub-DOM object.
$element = $dom->:removeAttribute("target");            //Removes attribute. Returns TRUE or FALSE.