How to identify non-unique email addresses via PHP

As mentioned in the title, the focus of this article is to identify non-unique email addresses through PHP. In other words, output duplicate email addresses through PHP.

First of all, I will give you a brief introduction to email:

→E-mail is a communication method that uses electronic means to exchange information. It is the most widely used service on the Internet. Through the network's email system, users can contact network users in any corner of the world at a very low price and very quickly.

The email format is usually username@xxx.com, where username is the username, which can be letters/numbers/underscores, and xxx is the domain name.

After a brief understanding of email, we went straight to the topic!

Specific problem description: How to write a PHP program to identify non-unique email addresses?

The PHP program code is as follows:

<?php
function array_not_unique($my_array) {
    $same = array();
    natcasesort($my_array);
    reset ($my_array);

    $old_key    = NULL;
    $old_value    = NULL;
    foreach ($my_array as $key => $value) {
        if ($value === NULL) { continue; }
        if ($old_value == $value) {
            $same[$old_key]    = $old_value;
            $same[$key]        = $value;
        }
        $old_value    = $value;
        $old_key    = $key;
    }
    return $same;
}

$test_array = array();
$test_array[1]    = &#39;xyz@example.com&#39;;
$test_array[2]    = &#39;dse@example.com&#39;;
$test_array[3]    = &#39;xyz@example.com&#39;;
$test_array[4]    = &#39;mno@example.com&#39;;

var_dump(array_not_unique($test_array));

Output:

array (size=2)
  3 => string 'xyz@example.com' (length=15)
  1 => string 'xyz@example.com' (length=15)

See also:

In the above code, there is such a function that everyone needs to know, which is natcasesort() function number:

natcasesort()The function of the function is to use " The "natural sorting" algorithm sorts the array, and the key values ​​retain their original key names;

In the natural sorting algorithm, the number 2 is less than the number 10; in the computer sorting algorithm, 10 is less than 2 because "10" The first number in is less than 2.

Note: This function is not case-sensitive; if successful, the function returns TRUE, if failed, returns FALSE.

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