Using WordPress ‘is_email’ PHP filter

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The is_email WordPress PHP Filter allows you to modify the result of the is_email WordPress PHP function – for example if you want to customise what is a valid email address.

Usage

add_filter('is_email', 'your_custom_function', 10, 3);

function your_custom_function($is_email, $email, $context) {
    // Your custom code here
    return $is_email;
}

Parameters

  • $is_email (string|false): The email address if it successfully passed the is_email() checks, false otherwise.
  • $email (string): The email address being checked.
  • $context (string): Context under which the email was tested.

More information

See WordPress Developer Resources: is_email

Examples

Allow only specific domain for email addresses

Allow email addresses only from the “example.com” domain.

add_filter('is_email', 'allow_specific_domain', 10, 3);

function allow_specific_domain($is_email, $email, $context) {
    $allowed_domain = 'example.com';
    $email_domain = substr(strrchr($email, "@"), 1);

    if ($email_domain === $allowed_domain) {
        return $is_email;
    } else {
        return false;
    }
}

Block a specific email address

Block an email address “[email protected]“.

add_filter('is_email', 'block_specific_email', 10, 3);

function block_specific_email($is_email, $email, $context) {
    $blocked_email = '[email protected]';

    if ($email === $blocked_email) {
        return false;
    } else {
        return $is_email;
    }
}

Change the minimum length of an email address

Allow email addresses with a minimum length of 6 characters.

add_filter('is_email', 'change_minimum_email_length', 10, 3);

function change_minimum_email_length($is_email, $email, $context) {
    $min_length = 6;

    if (strlen($email) >= $min_length) {
        return $is_email;
    } else {
        return false;
    }
}

Log invalid email addresses

Log invalid email addresses to a file.

add_filter('is_email', 'log_invalid_email', 10, 3);

function log_invalid_email($is_email, $email, $context) {
    if (!$is_email) {
        error_log("Invalid email: $email (Context: $context)\n", 3, 'invalid_emails.log');
    }
    return $is_email;
}

Convert email addresses to lowercase

Ensure that all email addresses are lowercase.

add_filter('is_email', 'convert_email_to_lowercase', 10, 3);

function convert_email_to_lowercase($is_email, $email, $context) {
    if ($is_email) {
        return strtolower($email);
    } else {
        return $is_email;
    }
}