array_diff() and array_intersect()

[phence]

When i found these two functions existed i almost backflipped! anyway...
but i don't quite understand something about them...

looking at the php manual example:

<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);

print_r($result);

//this will print:
//Array
//(
//    [1] => blue
//)
//
?>

What about yellow? I don't understand why this wouldn't print a difference there also?

the array_intersect() fucntion example (i won't repeat it here) picks up the common parts and excludes all the uncommom.... duh!

but why doesn't array_diff() pick up all the uncommon? would re-arranging

$result = array_diff($array1, $array2); 
//to
$result = array_diff($array2, $array1);

actually only print [1] => yellow ??

so if you wanted to find all the differnces you would have to then concantenate the the result like this?

$result_1_to_2 = array_diff($array1, $array2); 
$result_2_to_1 = array_diff($array2, $array1);
$all_differences = $result_1_to_2 . $result_2_to_1;

or is there a typo in the php manual... ?

Just want some clarification if you could.

Thank-you,
Phence

[phence]

ahhh... nevermind I'm an idiot.

[bpat1434]

I think this says it all:

PHP Manual :: array_diff wrote:

array_diff() returns an array containing all the values of array1 that are not present in any of the other arguments. Note that keys are preserved.

"Yellow" isn't in array1 now is it?

So yes, if you wanted to get the differences in both arrays, you could do that.

Or you could create your own function to do it:

function diff_array($array1, $array2, $array3=NULL)
{
	$ar3 = (is_array($array3))?TRUE:FALSE;

foreach($array1 as $a1)
{
	if(!in_array($a1, $array2))
	{
		$differences[] = $a1;
	}
}

foreach($array2 as $a2)
{
	if(!in_array($a2, $array1))
	{
		if(!in_array($a2, $differences))
		{
			$differences[] = $a2;
		}
	}
}

if($ar3)
{
	$array4 = array_merge_recursive($array1, $array2);
	foreach($array3 as $a3)
	{
		if(!in_array($a3, $array4))
		{
			if(!in_array($a3, $differences))
			{
				$differences[] = $a3;
			}
		}
	}
}

return $differences;
}

That works for me....

~Brett

[phence]

Well, it turns out that the functions work exactly how i needed it to...
At first glance i confused myself... when trying to work it all out with what i wanted to do.

<?
// Here's Kinda what I needed to do... and I figured it all out in the process.

$old_list = array("green", "red", "blue", "purple", "orange");
$new_list = array("green", "yellow", "red", "violet");
$deleted = array_diff($old_list, $new_list);
$added = array_diff($new_list, $old_list); 

echo "Deleted: "; print_r($deleted); echo "<p>";
echo "Added: "; print_r($added); echo "<p>";

echo "The OLD LIST was: green, red, blue, purple, orange" . "<br>";
echo "the NEW LIST was: green, yellow, red, violet" . "<p>";
echo "the DELETED should be: blue, purple and orange" . "<br>";
echo "the ADDED should be: yellow, violet" . "<p>";

/* OUTPUT

Deleted: Array ( [2] => blue [3] => purple [4] => orange ) 
Added: Array ( [1] => yellow [3] => violet ) 

The OLD LIST was: green, red, blue, purple, orange
the NEW LIST was: green, yellow, red, violet

the DELETED should be: blue, purple and orange
the ADDED should be: yellow, violet

*/

Thanks bpat for that other fuction... that will come in handy also!