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функция не описана

POP3::delete() public WP 1.0

Это метод класса: POP3{}

Хуков нет.

Возвращает

Null. Ничего.

Использование

$POP3 = new POP3();
$POP3->delete ( $msgNum );

Код POP3::delete() WP 5.5.1

wp-includes/class-pop3.php
<?php
function delete ($msgNum = "") {
    //  Flags a specified msg as deleted. The msg will not
    //  be deleted until a quit() method is called.

    if(!isset($this->FP))
    {
        $this->ERROR = "POP3 delete: " . _("No connection to server");
        return false;
    }
    if(empty($msgNum))
    {
        $this->ERROR = "POP3 delete: " . _("No msg number submitted");
        return false;
    }
    $reply = $this->send_cmd("DELE $msgNum");
    if(!$this->is_ok($reply))
    {
        $this->ERROR = "POP3 delete: " . _("Command failed ") . "[$reply]";
        return false;
    }
    return true;
}