note 74364 rejected from language.operators by danbrown

Note Submitter: mathiasrav at gmail dot com ---- <?php "This might be related to the comment 31-Oct-2006 07:20 just below, but here goes."; "I have found a bug (might be inherited from the way C does it) in PHP's operator precedence. Things like:"; if ($a != ($a = $b)) {/* more things */} "doesn't work. In my code, I've changed that to:"; if ($a != $b) {$a = $b; /* more things */} "A longer explanation (and a practical example) follows."; "I've written an IRC bot which (among other things) can parse an IRC string and find out how the individual characters are formatted."; // Quick guide to IRC formatting: In IRC, there are several 'format control characters', all non-printable. Among these are the bold formatting character, 0x02, which I'll write as <b>, and the underline formatting, 0x1F, which I'll write as <u>."; "My code parses a string and reads these characters and makes an array which contains the individual characters and their formatting."; "Here's an example. (I named the indices of the array, my code actually uses numbered indices)"; $ourstring = array( array( 'Hello ', 'bold' => 1, 'underline' => 0, ), array( 'world.', 'bold' => 0, 'underline' => 1, ) ); "And now, my formatparsedarray-to-ircstring function, that translates this to a string which can be posted to an IRC channel."; $resstring = ''; define('bold', "\x02"); define('underline', "\x1F"); $bold = false; $underline = false; foreach ($ourstring as $c) { if ($bold != ($bold = $c['bold'])) $resstring .= bold; if ($underline != ($underline = $c['underline'])) $resstring .= underline; $resstring .= $c[0]; } "Now, $resstring should contain:"; $resstring == "\x02Hello \x02\x1Fworld."; "However, it doesn't, since ($bold = $c\['bold'\]) is evaluated before ($bold == (...)). According to the operator precedence, == is evaluated left-to-right, and = is evaluated right-to-left, but in this case, == evaluated right-to-left."; "Is this a bug, or is it a leftover from C's way of parsing such things?"; ?>