Simplexml中的XML创建（php）

Question

I tried created an XML file using below code.

$xml = new SimpleXMLElement('<xml />');
while($rs = db_fetch_object($d_res)){
 $cmp = $xml->addChild('Company');
 $cmp->addChild('ID', $rs->nid);
 $cmp->addChild('Name', trim($rs->title));
 $cmp->addChild('Created', $rs->created);
 $cmp->addChild('Updated', $rs->changed);
}
header("Content-type: text/xml;charset=utf-8;");
print($xml->asXML());

But when I try to validate it I am getting below warnings

1. No DOCTYPE found! Checking XML syntax only.
2. No Character encoding declared at document level.

How to clear them? The XML is here and the validator used is validator.w3.org.

Answer 1

Although these are warnings that you could possibly ignore, it is indeed a good idea to try to fix them.

The first message indicates that the xml file doesn't specify any DTD; the second one refers to the fact that the xml directive doesn't contain any encoding attribute.

Unfortunately, from looking at the simplexml API, it doesn't look like it is possible to add either (although I might be missing something, not being familiar with it). I guess being “simple,” it is perfect for quickly read an xml file, but no so much to produce xml. You'll probaby have to turn to something slightly “heavier” like XML_Serializer .

Answer 2

You could decide to ignore these warnings. Neither a DOCTYPE nor a declared character encoding is required in XML. Actually, most XML documents do not contain a DOCTYPE.

A DOCTYPE is used for document validation , which means that a formal description exists what elements and attributes can exist for your document and a check can be made that your document does not contain anything else (in which case it would become invalid ). Unless you care for that and are prepared to develop, host and maintain your own DOCTYPE specification, ignore the warning.

Most of the time, creators and consumers of XML care about well-formedness , which means that the document adheres to the rules how XML needs to look like (no cross-nested tags, all tags must be closed, properly escaped content). Failing that, your document would simply break - but that's not the case here.

The character encoding warning is fixed by including an XML declaration at the top of your document that denotes the encoding:

<?xml version="1.0" encoding="utf-8" ?>

If you do not include it, XML defaults to "version 1.0" and "utf-8". If that's what you deliver anyway, all is well. If you deliver something else, it's necessary to include that info.

Answer 3

You can simply create the XML root element the next way:

$rootXml = new SimpleXMLElement("<!DOCTYPE your_root_xml_element SYSTEM 'URL_TO_DTD_SCHEME'><your_root_xml_element></your_root_xml_element>");
....
echo $rootXml->asXML();

This way you'll get the next valid XML:

<?xml version="1.0"?>
<!DOCTYPE your_root_xml_element SYSTEM "URL_TO_DTD_SCHEME">
<your_root_xml_element>
</your_root_xml_element>

Answer 4

$xml = new SimpleXMLElement('<?xml version="1.0" encoding="utf-8" ?>');

Answer 5

`$xmlstr = '<?xml version="1.0" encoding="utf-8"?>
<root>
<Data>
    <Id>0475109067</Id>
    <Contact>
        <Name>Daya</Name>
        <FirstName>Star</FirstName>
        <Email>test@test.com</Email>
    </Contact>
</Data>
<Result>
    <Name></Name>
</Result>
</root>';

$xml = new SimpleXMLElement($xmlstr); 
$xml->Result->Name = 'Xmltestfile'; 
$xml->asXML('test.xml');
$xml->asXML();`

This code will create a xml file with the name test