hi @cmb69 nice bug, I prefer unexpected terminology. Since the READ_CSV flag exists, the SplFileObject::current() method returns array or string or otherwise false. The SplFileObject class uses the alias __tostring (). Magic method __tostring() It is worth noting that prior to PHP 5.2.0 the __toString method was only called when combined directly with echo() or print(). As of PHP 5.2.0, it is called in any string context (e.g. in printf() with the% s modifier) ​​but not in other context types (e.g. with the% d modifier). Starting with PHP 5.2.0, converting objects without the __toString method to string would cause E_RECOVERABLE_ERROR. The first unexpected action is the magic method tostring() instead uses alias SplFileObject:: tostring(), the second unexpected action is SplFileObject::current() which does not return array although the bitmask for example 10 (e.g. READ_AHEAD | READ_CSV) uses READ_CSV. The third expected action is the modification of (alias of magic method __tostring()) SplFileObject::__tostring() if the bitmask uses READ_CSV accepts the input array and converts it to string

Pseudo code check:

<?php
$file = new SplFileObject(__FILE__, "rb");
echo 'string with key ' . $file->key();
echo $file->current(); // Bug, if SplFileObject::__tostring() alias of SplFileObject::fgets() next key
//$file->rewind(); // if SplFileObject::__tostring() alias of SplFileObject::fgets() or if SplFileObject::__tostring() alias of SplFileObject::current() for magic method __tostring() e.g. echo $file; now is array
$file->setFlags(SplFileObject::READ_CSV);
if(!is_array($file->current())) {
echo 'Not array' . "\r\n";
}
$flag_read_csv = 8 & $file->getFlags();
echo $file; // bug Magic method __tostring() and current(), is string
$file->setFlags(SplFileObject::READ_AHEAD | SplFileObject::READ_CSV);
$flag_read_csv2 = 8 & $file->getFlags();
$file->setFlags(0);
//$file->rewind(); // If SplFileObject::__current() don't update SplFileObject::__current()
if(is_array($file->current())) {
echo 'bug' . "\r\n";
}
var_dump('use flag READ_CSV:', $flag_read_csv, $flag_read_csv2);
?>

Output for 5.2.0 - 5.2.17, 5.3.0 - 5.3.29, 5.4.0 - 5.4.45, 5.5.0 - 5.5.38, 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.18, 7.3.0 - 7.3.5 (if SplFileObject::__tostring() alias of SplFileObject::current():

string with key 0<?php
Not array
<?php
string(18) "use flag READ_CSV:"
int(8)
int(8)

Expected result:

string with key 0<?php
<?php
string(18) "use flag READ_CSV:"
int(8)
int(8)