Sorting a multi-dimensional array

Anon

I've got an multidimensional array where the elements are arrays filled with strings.

I want to sort the whole array on an string in one element.

So the following array:

"a";"c";"b"
"b";"a";"c"
"c";"b";"a"

sorted on the second string, would become
"b";"a";"c"
"c";"b";"a"
"a";"c";"b"

The array is generated from a text file, so it's not a matter of correcting my SQL.

I was thinking about using the uasort function, but the documentation doesn't state what the sort function should return.

Does anyone know how to do this?

Thanks in advance
Eddie

Anon

The use of the uasort "function" is explained in the usort
manualpage.

try this:

function cmp($a,$b)
{
if ($a==$b) return 0;
if ($a>$b) return -1;
if ($a<$b) return 1;
};

$b=array(array(1,5,3,4),array(6,1,8,9));

for ($t=0;$t<count($b);$t++)
{
echo join(" ",$b[$t])."\n";
};

usort($b,"cmp");

for ($t=0;$t<count($b);$t++)
{
echo join(" ",$b[$t])."\n";
};

Anon

Or try

array-multisort($arr1, $arr2, $arr3 ...);

which does what you're saying, as long as you specify the array parameters in the right order.

Anon

I looked at that but couldn't get it to do what he wants.

How would you get this command to sort
an array of arrays by the value of the second field in each array?

Anon

Oops, yes, you're right - array_multisort is for several single field arrays. I've used this to sort a text file like this before, though -

In outline:

Read through the file, and "explode" each record into its separate fields. Add each field to a separate array.

So at the end of the file, we have as many arrays as fields.

Now you can use array_multisort to effectively sort the file on any of its fields. Depends what order you list the arrays as parameters.

$fp = fopen ("file.txt","r");
while ($data = fgets ($fp, 100)) {
$field = explode(";",$data);
$first[] = $field[0];
$second[] = $field[1];
$third[] = $field[2];
$fourth[] = $field[3];
}
fclose ($fp);
array_multisort ($second,$fourth,$first,$third);
for ($i=0; $i<count($second); $i++) {
echo "$first[$i] $second[$i] $third[$i] $fourth[$i]<br>";
}

Anon

I used the usort method and it works fine.
Thanks for all the advice,

Eddie