Tag: array

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PHP: Naturally sorting multidimension arrays by string values

This is just one of those things that I have to do often enough for it to be useful to have it close at hand, but not often enough that I actually remember how to do it.

I often run into this problem when using CakePHP, as results are returned from the database in a multidimensional array. Since MySQL doesn’t (as far as I’m aware) have an easy natural sort option, even if the results are sorted by name, strings that have numbers in can end up in the wrong order, e.g. “Item 10” before “Item 2”. Using a combination of usort() and strnatcasecmp(), it’s pretty easy to naturally sort an array by a value that appears in each subarray, like this:

usort($array, function($a, $b) {
    return strnatcasecmp($a['name'], $b['name']);
});

As an example, say I got the following array back from MySQL:

$array = array(
    array(
        'id' => 265,
        'name' => 'Drawer 1'
    ),
    array(
        'id' => 971,
        'name' => 'Drawer 10'
    ),
    array(
        'id' => 806,
        'name' => 'Drawer 2'
    ),
    array(
        'id' => 429,
        'name' => 'Drawer 20'
    )
);

“Drawer 10” comes before “Drawer 2”, which is obviously not what I want. Using strcasecmp() as the sort function on the above array wouldn’t change it, but using strnatcasecmp() gives the required result:

$array = array(
    array(
        'id' => 265,
        'name' => 'Drawer 1'
    ),
    array(
        'id' => 806,
        'name' => 'Drawer 2'
    ),
    array(
        'id' => 971,
        'name' => 'Drawer 10'
    ),
    array(
        'id' => 429,
        'name' => 'Drawer 20'
    )
);
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Copying Arrays (and Objects) in Javascript

This is a bit of an amateur mistake, but I definitely wasn’t the first person to make it and I suspect I won’t be the last. I had a JavaScript array that I wanted to copy, then make some change to the copy, so that I could access the original and the modified copy. Therefore, being used to PHP, I did the following, assuming it would make a ‘proper’ copy of the original:

var original = [1,2,3];  //Define original array
var copy = original;     //Attempt to copy original
copy[2] = 4;             //Modify the copy
alert(original[2]);      //Hoped for 3, got 4

I’d created a reference to the original array, rather than a copy of it. As a result, updating the copy also updated the original.

So, how do I create a copy of an array, rather than a reference. Thankfully, the slice method makes this very easy:

var original = [1,2,3];        //Define original array
var copy = original.slice(0);  //Copy original using slice
copy[2] = 4;                   //Modify the copy
alert(original[2]);            //Got 3 this time

This works fine for simple, one-dimensional arrays, where the array contains only booleans, numbers or strings. If the array is multi-dimensional, i.e. it contains other arrays or objects, then only the top level array will be copied, the arrays/objects it contains will be referenced. Therefore, it is necessary to create a function to do this – this seems to be a good way to do: http://my.opera.com/GreyWyvern/blog/show.dml/1725165

Alternatively, use jQuery, and take advantage of the extend method:

var original = {team:"Arsenal"};               //Define original object
var copy = jQuery.extend(true, {}, original);  //Copy original using extend
copy.team = "Man Utd" ;                        //Modify the copy
alert(original.team);                          //Alerts Arsenal