How do I sort alphanumeric array data correctly?

A human would often sort alphanumeric strings differently to the default functions in a computer language.

Therefore, when you want to sort such items as a human may, it is often referred to as natural sorting.

For instance, look at this output:


<?php

$numbers = array("1.gif","2.gif","20.gif","10.gif");

sort($numbers);

print_r($numbers);

?>

Array
(
[0] => 1.gif
[1] => 10.gif
[2] => 2.gif
[3] => 20.gif
)

If you were sorting the filenames in order, you would put 1.gif, 2.gif with 10.gif and 20.gif coming later. However the default sort algorithm doesn't do this, as you can see.

So if you want to sort in 'natural order' then you're in luck, because PHP provides the natsort function to save you having to write a clever function yourself, and this will do just what you want here:


<?php

$numbers = array("1.gif","2.gif","20.gif","10.gif");

natsort($numbers);

print_r($numbers);

?>

Which this time prints just what we're after:

Array
(
[0] => 1.gif
[1] => 2.gif
[3] => 10.gif
[2] => 20.gif
)

Note how it also maintains the keys, which is also often invaluable.

Comments on this Question/Answer

Natsort will sort while maintaining the keys, is there a way of doing the same sort without maintaining the keys?
By: Dave Rigby, 25 Apr 2009 18:03:06

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