Find numbers on a string and order by them

I have this string

$s = "red2 blue5 black4 green1 gold3";

I need to order by the number, but can show the numbers.
Numbers will always appears at the end of the word.
the result should be like:

$s = "green red gold black blue";

Thanks!

>Solution :

$s = "red2 blue5 black4 green1 gold3";
$a=[];
preg_replace_callback('/[a-z0-9]+/',function($m) use (&$a){
    $a[(int)ltrim($m[0],'a..z')] = rtrim($m[0],'0..9');
},$s);
ksort($a);
print " Version A: ".implode(' ',$a);

$a=[];
foreach(explode(' ',$s) as $m){
    $a[(int)ltrim($m,'a..z')] = rtrim($m,'0..9');
}
ksort($a);
print " Version B: ".implode(' ',$a);

preg_match_all("/([a-z0-9]+)/",$s,$m);
foreach($m[1] as $i){
    $a[(int)substr($i,-1,1)] = rtrim($i,'0..9');
}
ksort($a);
print " Version C: ".implode(' ',$a);

Use one of them, but also try to understand whats going on here.