XML Pretty Printer in PHP5

by Will Bond - March 15, 2007 / 1:12pm

Today I was working with debugging some XML, and needed a way to make the XML more readable. The following is a little function that should do the job for some simple XML, and you can probably tweak it to your needs. It uses PHP5's SimpleXMLElement object to parse and return the XML, then indents it in a logical way.

<?php
/**
* Takes xml as a string and returns it nicely indented
*
* @param string $xml The xml to beautify
* @param boolean $html_output If the xml should be formatted for display on an html page
* @return string The beautified xml
*/
function xml_pretty_printer($xml, $html_output=FALSE)
{
	$xml_obj = new SimpleXMLElement($xml);
	$xml_lines = explode("\n", $xml_obj->asXML());
	$indent_level = 0;
	
	$new_xml_lines = array();
	foreach ($xml_lines as $xml_line) {
		if (preg_match('#^(<[a-z0-9_:-]+((\s+[a-z0-9_:-]+="[^"]+")*)?>.*<\s*/\s*[^>]+>)|(<[a-z0-9_:-]+((\s+[a-z0-9_:-]+="[^"]+")*)?\s*/\s*>)#i', ltrim($xml_line))) {
			$new_line = str_pad('', $indent_level*4) . ltrim($xml_line);
			$new_xml_lines[] = $new_line;
		} elseif (preg_match('#^<[a-z0-9_:-]+((\s+[a-z0-9_:-]+="[^"]+")*)?>#i', ltrim($xml_line))) {
			$new_line = str_pad('', $indent_level*4) . ltrim($xml_line);
			$indent_level++;
			$new_xml_lines[] = $new_line;
		} elseif (preg_match('#<\s*/\s*[^>/]+>#i', $xml_line)) {
			$indent_level--;
			if (trim($new_xml_lines[sizeof($new_xml_lines)-1]) == trim(str_replace("/", "", $xml_line))) {
				$new_xml_lines[sizeof($new_xml_lines)-1] .= $xml_line;
			} else {
				$new_line = str_pad('', $indent_level*4) . $xml_line;
				$new_xml_lines[] = $new_line;
			}
		} else {
			$new_line = str_pad('', $indent_level*4) . $xml_line;
			$new_xml_lines[] = $new_line;
		}
	}
	
	$xml = join("\n", $new_xml_lines);
	return ($html_output) ? '<pre>' . htmlentities($xml) . '</pre>' : $xml;
}
?>

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About the Author

Will Bond, Senior Technical Architect

I’m involved with pretty much anything computer related here at iMarc, from servers to coding and markup best practices. I’m also the unofficial resident open source advocate.

After work I spend time with my awesome wife and daughter in and around our home in beautiful Newbury, MA.
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