PHP：查找值的数组差异[重复]

Question

This question already has an answer here:

• Removing array item by value 10 answers

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

$oldmail and $newmail.

Both looks like this:

[0] => [e-mail]
[1] => [e-mail]
[2] => [e-mail]
...

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?

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Answer 1

PHP code demo

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

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