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[dmorison]

You have 4 variables: $a, $b, $c and $d.

What's most efficient way to check that they ALL contain different values?

I'll post my entry once i've had a crack at it... :)

[justageek]

Maybe this:

$myarray[] = $a;
$myarray[] = $b;
$myarray[] = $c;
$myarray[] = $d;

$myuniquearray = array_unique($myarray);

if(count($myarray) <> count($myuniquearray)){
// There are dupes
}else{
// They are all different
}

JAG

[surfin2u]

how about:

$arr = array();
$arr[$a] = 1;
$arr[$b] = 1;
$arr[$c] = 1;
$arr[$d] = 1;
if (count($arr) == 4)
echo "all different";

[FalseDawn]

With only 4 values, I'd just do a straight compare:

if ($a!=$b && $a!=$c && $a!=$d && $b!=$c && $b!=d && $c!=$d) {all different}

[surfin2u]

...and I thought my solution was so clever, but FalseDawn I think that you've hit the nail on the head!

[justageek]

I guess I'm always thinking scalability ;-)

JAG

[surfin2u]

I guess I'm always thinking scalability ;-)

requirements first, scalability only if required... ;-)

I think my solution is fastest when a larger amount of data is involved.

[ergophobe]

How about this if you want it to scale *and* you have lots of data in each variable.

$size = count($data_array);

for ($i=0; $i<$size; $i++)
{
$key = md5($data_array[$i]);
$unique_array[$key] = 1;
}

At least that way you won't end up trying to create a 600 character array key.

[surfin2u]

At least that way you won't end up trying to create a 600 character array key.

What's wrong with a 600 character array key?

[ergophobe]

Okay, you won't be trying to make a 1.2MB array key.

Raises an interesting question: what is the limit on the size of an array key? Is it just a function of system memory? An array index is merely a string and the manual says

Note: It is no problem for a string to become very large. There is no practical bound to the size of strings imposed by PHP, so there is no reason at all to worry about long strings.

So I take it back. Go ahead and index your arrays using the contents of a volume of the Encyclopedia Britannica. Looks like it should be okay ;-)

[surfin2u]

PHP arrays are the greatest!