How to sort xpath using php

Question

i searched through the website and couldnt find exact result for my question.

i need to search through the xml file and sort the output by the order in date descending.

<?xml version="1.0"?>
<entries>
  <entry>
    <date>1299565881</date>
    <action>made an action under category</action>
    <user>Admin</user>
  </entry>
  <entry>
    <date>1299566115</date>
    <action>Item deleted</action>
    <user>Admin</user>
  </entry>
</entries>

here is my code

<?php

$data = simplexml_load_file($filename);

if($to_date_int>$global_date)
    $op = $data->xpath('/entries/entry[date<='.$to_date_int.']');
else
    $op = $data->xpath('/entries/entry');

Thanks in advance..

What kind of output are you expecting? You want to sort each entry by date, then what? — Rusty Fausak
– Rusty Fausak, Commented Sep 28, 2011 at 5:52
XPath is not a good tool for sorting, either pre-sort with XSLT or post-sort with PHP. — salathe
– salathe, Commented Sep 28, 2011 at 6:31

salathe · Accepted Answer · 2011-09-28 06:36:23Z

3

Since $op will be an array of the matching entry elements, you could use PHP's array sorting functions to sort by their associated date elements.

function sort_entries_by_date($a, $b) {
    return (int) $b->date - (int) $a->date;
}
usort($op, 'sort_entries_by_date');

^{(If you're using PHP 5.3, the named function could be placed by an inline anonymous function.)}

answered Sep 28, 2011 at 6:36

salathe

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2 Comments

vijay Over a year ago

Works fine., thank u salathe., Can u explain me how does the function actually works !? what happens in the line return (int)$b->date - (int)$a->date; Thanks again.

salathe Over a year ago

The sort function must return 0 if the values are to be considered the same, less than zero if $a is to appear lower than $b in the sorted array, or greater than zero otherwise ($a will appear higher than $b). So my function will sort the entries by descending date order (because if the date in $a is greater than that in $b, the function will return a negative number). As for the maybe strange (int)$b->date syntax, that's just getting the integer value of the <date> element belonging to the <entry> held in $b.

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