Re: PHP 4.0 Bug #9482 Updated: || operator gives unexpected results

Thanks. I thought that or and || were identical. Guess not. Steve Bug Database wrote: > > ID: 9482 > Updated by: torben > Reported By: ssegarra@mitre.org > Old-Status: Open > Status: Closed > Bug Type: *General Issues > Assigned To: > Comments: > > This isn't a bug; it's a result of the differing precedence for || and or (which > are otherwise identical, btw). > > Try this: > > $db = mysql_connect("localhost", "root") || print "error > connecting"; > echo $db; > > The output should be '1'. The reason is that || has higher precedence than =, > so PHP sees the above statement as: > > $db = (mysql_connect("localhost", "root") || print "error > connecting"); > > ...which means that $db is assigned the value of the expression in parens, which > in this case will always evaluate to 1, which is not a valid MySQL resource. > > Next try this: > > ($db = mysql_connect("localhost", "web")) || print "error connecting > "; > echo $db; > > The output should be 'Resource id #1', since the precedence has now been forced. > The other way to force precedence is to use the lower-precedence 'or', as you > mentioned. > > The operator precedence table can be found in the manual at: > > > http://www.php.net/manual/en/language.operators.precedence.php > > Hope this helps, > > Torben > > Previous Comments: > --------------------------------------------------------------------------- > > [2001-02-27 10:52:12] ssegarra@mitre.org > <? > > $db = mysql_connect("localhost", "web") || print "error connecting > ".mysql_error()." ".mysql_errno(); > mysql_select_db("surveys"); > > $result = mysql_query("select * from attract") || print "error querying > ".mysql_error()." ".mysql_errno(); > > $i = 0; > while ($row = mysql_fetch_array($result)){ // && ($i++ < 5)){ > echo $row[0]." ".$row[1]."<br>"; > } > ?> > > this script will repeatedly give me invalid MySQL Link Resource Warnings, but by changing the > "||" to "or" it will work fine. > > Thanks > > --------------------------------------------------------------------------- > > ATTENTION! Do NOT reply to this email! > To reply, use the web interface found at > http://bugs.php.net/?id=9482&edit=2