https://stackoverflow.com/questions/20339726
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RussianBefore you can sort the data, you need to create an array which contains as its values the separate items you want to sort. From your debug outputs, these are multiple <reservation> nodes in the input XML, which are children of the element represented by $array/$this->data in those samples (it doesn't matter if it's the root of the document or not, SimpleXML has no Document object).
Your print_r and var_dump output shows that you do not currently have such an array, only a SimpleXML object:
- Your first example shows
var_dump($array)giving output beginningobject(SimpleXMLElement)#275 (1) {- ignore the wordarrayfurther in, that's just howvar_dumpis rendering the insides of the object. - Later, you have a
print_r($array);beginningarray(1) {- but this is only because you've wrapped the real data in a single-element array on the line above ($array = array($this->data);) and that one element ($array[0]) shows asobject(SimpleXMLElement)#280 (1) { ....
Note that there's no need to go further and convert all the inner SimpleXML objects into arrays - you just need a list that is sortable, containing the items you are interested in. I would personally use a simple and explicit foreach loop, for maximum code readability, although "cleverer" solutions are available.
Once you have a sortable list, you need a callback function for usort which compares its two parameters. The attempt you've made is along the right lines, but refers to the non-existent (in that function) variable $array; the values you need to compare are the function's arguments, which you've called $a and $b - specifically, you want to compare strtotime($a->event_start_dt) with strtotime($b->event_start_dt).
You can also make the function much simpler, because it follows the common misconception that the return value of the callback should be -1, 0, or 1. In fact, it can be any integer, and only its sign matters - returning -42 will have the same effect as returning -999, namely placing item $a before $b in the resulting array.
I can't easily give a tested example, because you haven't provided the underlying XML to reproduce your input (e.g. echo $this->data->asXML();), but the basic approach I would take would be this:
// Start with an empty array, and add all the items we're interested in to it
$sortable_array = array();
// Loop over all <reservation> children of the SimpleXML object $this->data
// See http://php.net/manual/en/simplexml.examples-basic.php
foreach ( $this->data->reservation as $reservation_node )
{
// Add the individual node to our array
$sortable_array[] = $reservation_node;
}
// Now let's sort out the callback function for the sorting
// This could also be an anonymous function passed directly to usort
function sort_callback_event_start($a, $b)
{
// $a and $b are both items in our $sortable_array, and therefore
// <reservation> nodes which we expect to each have a child
// called <event_start_dt>
// If we convert both dates to Unix timestamps, we have two integers
// to compare, and a simple subtraction gives the desired result
// of <0, 0, or >0 as documented at http://php.net/usort
return
strtotime((string)$a->event_start_dt)
-
strtotime((string)$b->event_start_dt);
}
// Now, we have everything we need to do the actual sorting
usort($sortable_array, 'sort_callback_event_start');
// $sortable_array is now sorted as desired! :D
// Note that the items within it are still SimpleXML objects,
// so you still need to access their properties to do something useful
// e.g. some HTML output with the names listed in order of their start date:
echo '<ol>';
foreach ( $sortable_array as $reservation_node )
{
echo '<li>', (string)$reservation_node->event_name, '</li>';
}
echo '</ol>';
