sort associative array codeigniter php - php

Question

Here is what I want to do:
$newArray = array();
foreach($student as $s){
$newArray[$s->id][$s->grade] = $s;
}
I want to sort the students by their grades (more of a group than a sort) but I just want the grades to be sorted not the id. I could have don't this:
$newArray[$s->id] = $s->grade
asort($newArray)
but I need the remaining data in $s. Also, there is huge chunk of data associated with each student which I want to maintain.
How can I achieve such a sorting?

Answer 1

Edit:
Sine you're working in a framework, best declare your sort callback as a member function (inside the same class as where you'll be needing it, of course):
private function sortCB(array $a, array $b)
{//the array type hinting in arguments is optional
$i = array_keys($a);//but highly recommended
$j = array_keys($b);
if (end($i) === end($j))
{
return 0;
}
//replace '>' with '<' if you want to sort descending
return (end($i) > end($j) ? 1 : -1);//this is ascending
}
Then, in the method where the actual sorting is needed:
uasort($theArray,array($this,'sortCB'));
For more examples, see the docs. I've added a full class example at the end of this (bulky) answer
I've tried this on writecodeonline, which isn't all too good at this kind of stuff, but this did work:
$foo = array_fill_keys(array('foo','bar','q','Bond'),array());
$i = '256';
foreach($foo as $k=>$v)
{
$foo[$k][$i] = $k;
$i = (string)((int)$i%2 === 0 ? ((int)$i/2)+1 : (int)$i*3);
}
function sortCB($a,$b)
{
$i = array_keys($a);
$j = array_keys($b);
if (end($i) === end($j))
{
return 0;
}
return (end($i) > end($j) ? 1 : -1);
}
uasort($foo,'sortCB');
var_dump($foo);
But since you're using a framework, you might do well declaring that function as a member function private function sortCB(array $a,array $b), and use it like so:
uasort($foo,array($this, 'sortCB'));
There might be some more info on how best to use this callback function in a class context here
Full example + usage (tested and working):
class test
{
public $foo = null;
public function __construct()
{
$this->foo = array_fill_keys(array('foo','bar','q','Bond'),array());
$i = '256';
foreach($this->foo as $k=>$v)
{
$this->foo[$k][$i] = $k;
$i = (string)((int)$i%2 === 0 ? ((int)$i/2)+1 : (int)$i*3);
}
}
private function sortCB($a,$b)
{
$i = array_keys($a);
$j = array_keys($b);
if (end($i) === end($j))
{
return 0;
}
return (end($i) > end($j) ? 1 : -1);
}
public function sortFoo()
{
uasort($this->foo,array($this,'sortCB'));
print_r($this->foo);
return $this->foo;
}
}
$bar = new test();
$arr = $bar->sortFoo();

Answer 2

You can do something like:
foreach($student as $s){
$newArray[$s->id] = $s;
}
usort($newArray, function ($a, $b) { return $a->grade - $b->grade; });
Edit
For later versions that don't support anonymous functions you can define comparison function first:
function sortByGrade($a, $b)
{
return $a->grade - $b->grade;
}
usort($newArray, 'sortByGrade');
But if you get this data from db it would be easier to order it in your sql query. If you use ORM you can use its associated method.