format xml string - php

Question

What is the best way to format XML within a PHP class.
$xml = "<element attribute=\"something\">...</element>";
$xml = '<element attribute="something">...</element>';
$xml = '<element attribute=\'something\'>...</element>';
$xml = <<<EOF
<element attribute="something">
</element>
EOF;
I'm pretty sure it is the last one!

Answer 1

With DOM you can do
$dom = new DOMDocument;
$dom->preserveWhiteSpace = FALSE;
$dom->loadXML('<root><foo><bar>baz</bar></foo></root>');
$dom->formatOutput = TRUE;
echo $dom->saveXML();
gives (live demo)
<?xml version="1.0"?>
<root>
<foo>
<bar>baz</bar>
</foo>
</root>
See DOMDocument::formatOutput and DOMDocument::preserveWhiteSpace properties description.

Answer 2

This function works perfectlly as you want you don't have to use any xml dom library or nething just pass the xml generated string into it and it will parse and generate the new one with tabs and line breaks.
function formatXmlString($xml){
$xml = preg_replace('/(>)(<)(\/*)/', "$1\n$2$3", $xml);
$token = strtok($xml, "\n");
$result = '';
$pad = 0;
$matches = array();
while ($token !== false) :
if (preg_match('/.+<\/\w[^>]*>$/', $token, $matches)) :
$indent=0;
elseif (preg_match('/^<\/\w/', $token, $matches)) :
$pad--;
$indent = 0;
elseif (preg_match('/^<\w[^>]*[^\/]>.*$/', $token, $matches)) :
$indent=1;
else :
$indent = 0;
endif;
$line = str_pad($token, strlen($token)+$pad, ' ', STR_PAD_LEFT);
$result .= $line . "\n";
$token = strtok("\n");
$pad += $indent;
endwhile;
return $result;
}

Answer 3

//Here is example using XMLWriter
$w = new XMLWriter;
$w->openMemory();
$w->setIndent(true);
$w->startElement('foo');
$w->startElement('bar');
$w->writeElement("key", "value");
$w->endElement();
$w->endElement();
echo $w->outputMemory();
//out put
<foo>
<bar>
<key>value</key>
</bar>
</foo>

Answer 4

The first is better if you plan to embed values into the XML, The second is better for humans to read. Neither is good if you intend really work with XML.
However if you intend to perform a simple fire and forget function that takes XML as a input parameter, then I would say use the first method because you will need to embed parameters at some point.
I personally would use the PHP class simplexml, it's very easy to use and it's built in xpath support makes detailing the data returned in XML a dream.