function obfuscate_email($email)
{
    $em   = explode("@",$email);
    $name = implode(array_slice($em, 0, count($em)-1), '@');
    $len  = floor(strlen($name)/2);

    return substr($name,0, $len) . str_repeat('*', $len) . "@" . end($em);   
}

// to see in action:
$emails = ['"Abc\@def"@iana.org', 'abcdlkjlkjk@hotmail.com'];

foreach ($emails as $email) 
{
    echo obfuscate_email($email) . "\n";
}

Vystup:

"Abc\*****@iana.org
abcdl*****@hotmail.com

Metoda2:

<?php

    /*

    Here's the logic:

    We want to show X numbers.
    If length of STR is less than X, hide all.
    Else replace the rest with *.

    */

function mask($str, $first, $last) {
    $len = strlen($str);
    $toShow = $first + $last;
    return substr($str, 0, $len <= $toShow ? 0 : $first).str_repeat("*", $len - ($len <= $toShow ? 0 : $toShow)).substr($str, $len - $last, $len <= $toShow ? 0 : $last);
}

function mask_email($email) {
    $mail_parts = explode("@", $email);
    $domain_parts = explode('.', $mail_parts[1]);

    $mail_parts[0] = mask($mail_parts[0], 2, 1); // show first 2 letters and last 1 letter
    $domain_parts[0] = mask($domain_parts[0], 2, 1); // same here
    $mail_parts[1] = implode('.', $domain_parts);

    return implode("@", $mail_parts);
}

$emails = array(
    'a@a.com',
    'ab@aa.com',
    'abc@aaa.com',
    'abcd@aaaa.com',
    'abcde@aaaaa.com',
    'abcdef@aaaaaa.com',
    'abcdefg@aaaaaaa.com',
    'abcdefgh@aaaaaaaa.com',
    'abcdefghi@aaaaaaaaa.com'
);

foreach ($emails as $email){
    echo '<b>'.$email.'</b><br>'.mask_email($email).'<br><hr>';
}

vystup:

a@a.com
*@*.com

ab@aa.com
**@**.com

abc@aaa.com
***@***.com

abcd@aaaa.com
ab*d@aa*a.com

abcde@aaaaa.com
ab**e@aa**a.com

abcdef@aaaaaa.com
ab***f@aa***a.com

abcdefg@aaaaaaa.com
ab****g@aa****a.com

abcdefgh@aaaaaaaa.com
ab*****h@aa*****a.com

abcdefghi@aaaaaaaaa.com
ab******i@aa******a.com

Zdroj:

https://stackoverflow.com/questions/20545301/partially-hide-email-address-in-php

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