Looks like this function has exactly the same behavior as base64_decode($test, true) -> it returns FALSE if $text contains characters outside the Base64 alphabet, although this isn't documented here.
(PHP 4, PHP 5, PHP 7, PHP 8)
imap_base64 — Decode BASE64 encoded text
$string): string|false
Decodes the given BASE-64 encoded string.
stringThe encoded text
Returns the decoded message as a string, 或者在失败时返回 false.
Looks like this function has exactly the same behavior as base64_decode($test, true) -> it returns FALSE if $text contains characters outside the Base64 alphabet, although this isn't documented here.