Parsing XML data with php - php

Question

I am trying to pull text from a single element in an xml file, i was able to pull the entire file but i really only need a couple of lines from the file...
On this page i was able to pull the entire xml file ( http://smyrnainlet.com/testing.php )
But when i try to just single out one line from that file.
http://smyrnainlet.com/current_data.php
This is the error i am receiving:
Fatal error: Call to a member function getbyElementID() on a non-object in /home/content/74/8620474/html/current_data.php on line 9
If anyone could help me that would be amazing, i have been struggling with this for hours.
This is my code:
<?php
function startElemHandler($parser, $name, $attribs)
{
if (strcasecmp($name, "current_observation") ==0 ) {
echo "<div id='waves'>\n";
}
if (strcasecmp($name, "wave_height_ft") ==0) {
$waveHeight->getbyElementID("wave_height_ft");
echo $waveHeight->asXML();
}
}
function endElemHandler($parser, $name)
{
if (strcasecmp($name, "current_observation") ==0 ) {
echo "</div>";
}
}
$parser = xml_parser_create();
xml_set_element_handler($parser, startElemHandler, endElemHandler);
xml_parser_set_option($parser, XML_OPTION_CASE_FOLDING, 0);
$strXML = implode("",file("http://www.weather.gov/xml/current_obs/41009.xml"));
xml_parse($parser, $strXML);
xml_parser_free($parser);
?>

Answer 1

You have a few fundamental flaws with your code but you are essentially asking how to parse an XML file. I suggest using PHP's DOMDocument with DOMXPath to extract the data you need. Here is some example code:
$xml = file_get_contents('weather.xml');
$dom = new DOMDocument();
#$dom->loadHTML($xml);
$domx = new DOMXPath($dom);
$entries = $domx->evaluate("//wave_height_ft");
$arr = array();
foreach ($entries as $entry) {
$arr[] = '<' . $entry->tagName . '>' . $entry->nodeValue . '</' . $entry->tagName . '>';
}
print_r($arr);

Answer 2

$waveHeight seem not defined (not in scope) wher you try to use it!
you can
pass it as argument
use the global statement
create a class