Alright, after playing a while, I'm confident the following replacement function works in all cases, including the ones for which the native fputcsv function fails. If fputcsv fails to work for you (particularly with mysql csv imports), try this function as a drop-in replacement instead.
Arguments to pass in are exactly the same as for fputcsv, though I have added an additional $mysql_null boolean which allows one to turn php null's into mysql-insertable nulls (by default, this add-on is disabled, thus working identically to fputcsv [except this one works!]).
<?php
function fputcsv2 ($fh, array $fields, $delimiter = ',', $enclosure = '"', $mysql_null = false) {
$delimiter_esc = preg_quote($delimiter, '/');
$enclosure_esc = preg_quote($enclosure, '/');
$output = array();
foreach ($fields as $field) {
if ($field === null && $mysql_null) {
$output[] = 'NULL';
continue;
}
$output[] = preg_match("/(?:${delimiter_esc}|${enclosure_esc}|\s)/", $field) ? (
$enclosure . str_replace($enclosure, $enclosure . $enclosure, $field) . $enclosure
) : $field;
}
fwrite($fh, join($delimiter, $output) . "\n");
}
?>