WordPress at a glance
function is not described

POP3::is_ok() public WP 1.0

The following methods are internal to the class.

{} It's a method of the class: POP3{}

No Hooks.

Return

Null. Nothing.

Usage

$POP3 = new POP3();
$POP3->is_ok ( $cmd );

Code of POP3::is_ok() WP 5.5.1

<?php
function is_ok ($cmd = "") {
    //  Return true or false on +OK or -ERR

    if( empty($cmd) )
        return false;
    else
        return( stripos($cmd, '+OK') !== false );
}