Looks like this function has exactly the same behavior as base64_decode($test, true) -> it returns FALSE if $text contains characters outside the Base64 alphabet, although this isn't documented here.
(PHP 4, PHP 5, PHP 7, PHP 8)
imap_base64 — Base64 kodlu dizgeyi 8 bitlik dizgeye dönüştürür
Base-64 kodlu dizge dizgesini 8 bitlik bir dizgeye
dönüştürür.
metinBase64 kodlu metin.
8 bitlik bir dizge, başarısızlık durumunda false döner.
Looks like this function has exactly the same behavior as base64_decode($test, true) -> it returns FALSE if $text contains characters outside the Base64 alphabet, although this isn't documented here.