Sends an email. Parameters: Receiver, or receivers of the mail. The formatting of this string must comply with RFC 2822.

Actually no. What you're missing is that PHP itself does not send the email. It goes through sendmail (and whatever application that may be). MTAs will convert ...

imap_rfc822_write_address — Returns a properly formatted email address given the mailbox, host, and personal info

DateTimeInterface was created so that parameter, return, or property type declarations may accept either DateTimeImmutable or DateTime as a value.

Representation of date and time. This class behaves the same as DateTimeImmutable, except objects are modified itself when modification methods such as DateTime ...

Returns date formatted according to given format. Parameters: The format of the outputted date string. See the formatting options below.

Parses a » RFC 822 compliant recipient list, such as that found in the To: header. Parameters ¶. addresses. A string containing addresses, like in: Wez Furlong ...

RFC2822 says that it must be accepted, but should be ignored in routing. Note that if an address doesn't contain a personal part, or an "at domain list ...

This page describes the different date/time formats in a BNF-like syntax, that the DateTimeImmutable, DateTime, date_create(), date_create_immutable(), and ...

RFC 2822 allows for email addresses like user@localhost or user@example. But, RFC 2821 (SMTP Standard) does not allow for those. See ...