I slammed into this whilst converting Access data into MySQL.

I was attempting to break apart the following into words (* here indicates that it fails to match /[\w,.-?]/):

|*|W|a|s|h|i|n|g|t|o|n|,|*|D|C|*|*     // text
057617368696e67746f6e2c20444320200     // hex

I first tried splitting on any white space or commas:

preg_match( '/[\\s,]+/', $string, PREG_SPLIT_NO_EMPTY );

When this didn't work, I examined the hexadecimal values as above, and, assuming that control characters weren't included in the \s group, tried several things, including the very simple:

preg_match( '/\\W/', $string, PREG_SPLIT_NO_EMPTY );

Nothing worked, and ultimately I had to use preg_match_all() to split the string up.

Example:

$string = chr(5) . 'Washington,' . chr(4) . 'DC' . chr(2);
$parts = preg_split( '/\\W/', $string, PREG_SPLIT_NO_EMPTY );
echo join('|', $parts);