entry_212_CA60CTF_2014-10-30_12-14-57.jpg

<?xml version="1.0"?>
<Incidents xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" Count="3" Date="2014-10-30" Time="12:14:57" FileName="2014-10-30_dones_Hillsborough_Leisure_Centre.xml">
  <Incident>
    <EntryTime>2014-08-16T08:54:12</EntryTime>// want to group by this element
    <ExitTime>2014-08-16T17:03:51</ExitTime>
 </Incident>

if(file_exists($xmlFullFilename)) {
            $xmlDoc = new DomDocument();
            $xmlDoc->load($xmlFullFilename);
            $tmp = $xmlDoc->getElementsByTagName("Incidents");
            $root = $tmp->item(0);
}

eg:<EntryTime>2014-08-16T08:46:17</EntryTime>...

          $tmp = split(" ", $entryTime);
                $dateString = $tmp[0] . "T" . $tmp[1];
                $entryTimeNode = $xmlDoc->createElement("EntryTime", $dateString);

$dom = new DomDocument();
$dom->loadXML( get_xml() );

$xp = new DOMXPath( $dom );

$d_list = array();

# get all EntryTime nodes in the document
foreach ($xp->query("Incident/EntryTime") as $x) {
    # take a substring of the nodeValue corresponding to the date, put it in an array
    $d_list[ substr( $x->nodeValue, 0, 10 ) ] = 1;
}

# $d_list now contains every date referenced in the file
# if you only want the Incidents for a certain date, you obviously don't need to use
# use a foreach loop!
foreach ($d_list as $d => $v) {
    # select every EntryTime node where the value starts with $d
    # the /.. at the end returns its parent node, i.e. the Incident node
    foreach ($xp->query("Incident/EntryTime[starts-with(.,'$d')]/..") as $node) {
        # now do whatever you want with the Incident node data
        print_r($node);

    }
}