PHP: Find array difference on values

Question

I have two pretty big arrays with email addresses in them.

$oldmail and $newmail.

Both looks like this:

[0] => some@email.com
[1] => some1@email.com
[2] => some2@email.com
...

I want to find all the email values in $newmail that does not exist anywhere in $oldmail.

I think this should work:

foreach ($oldmail as $key => $value) 
{
    foreach ($newmail as $key2 => $value2) 
    {
        if ($value == $value2) 
        {
            //do nothing..
        }
        else
        {
            echo $value2;
        }
    }
}

But it is way to resource heavy with big lists.

Is there another more effecient way I can do this?

I tried array_diff but it does not seam to search through all values - only compares value[0] vs. value2[0] if I understand correct? It shoud compare value[0] against all values in the other array — Bolli, Mar 24 '17 at 13:56
Ahh thats why array_diff() didnt work before, I forgot to strtolower() all the strings :) Thanks! — Bolli, Mar 24 '17 at 14:04
@Bolli, accept one of the answers or delete your question if your problem is resolved. Thanks, — Abhay Maurya, Mar 24 '17 at 14:30

score 4 · Accepted Answer · answered Mar 24 '17 at 13:56

4

PHP code demo

<?php
$a1=array("red","green","blue","yellow");
$a2=array("red","green","blue");

$result=array_diff($a1,$a2);
print_r($result);
?>

answered Mar 24 '17 at 13:56

Sahil Gulati

15,028
4
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score 1 · Answer 2 · answered Mar 24 '17 at 14:00

1

Use array_diff in PHP

$a1=array("some@email.com","some1@email.com");
$a2=array("some1@email.com","some2@email.com");
$result=array_diff($a2,$a1);
print_r($result);

Result:

Array ( [1] => some2@email.com )

answered Mar 24 '17 at 14:00

Ramalingam Perumal

1,367
2
17
46

Why did you copy the other answer? – Mihai Matei Mar 24 '17 at 14:02
thats just the snippet from the official php manual entry for array_diff. They probably both just copied that from there. – GDY Aug 27 '22 at 08:06

score 1 · Answer 3 · answered Mar 24 '17 at 14:02

1

array_diff() is right choice. It doesn't only matches by index as you mentioned in your comment. It compares all values.

Give this a shot:

$result=array_diff($newmail,$oldmail);
print_r($result);

answered Mar 24 '17 at 14:02

Abhay Maurya

11,819
8
46
64

PHP: Find array difference on values

3 Answers3