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Bug #18645 dot-operator allows bogus operations with shortcut for if
Submitted: 2002-07-30 09:01 UTC Modified: 2002-07-30 11:45 UTC
From: alpha at rrs dot at Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 4.2.1 OS: windows 2000
Private report: No CVE-ID: None
View Developer Edit
 [2002-07-30 09:01 UTC] alpha at rrs dot at 
given this code
<?php

$var = 5;

echo "string1 ".empty($var)?0:$var." string2";
// output "0" - WRONG
echo "<br>";
echo "string1 ".(empty($var)?0:$var)." string2<br>";
// output "string1 5 string2"
echo "<br>";

echo 'string1 '.empty($var)?0:$var.' string2';
// output "0" - WRONG
echo '<br>';
echo 'string1 '.(empty($var)?0:$var).' string2<br>';
// output "string1 5 string2"
echo '<br>';

?>

I get an error-message if I try 
echo 'string1 '.empty($var)?0.' string2';
or just 
echo 'string1 '.0.' string2';
, thus there is a missing error check at parse time. I don't know enough about the internal functions of PHP to say if it's the scripting engine or something else. See yourself ...

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 [2002-07-30 11:43 UTC] m dot ford at lmu dot ac dot uk 
Let's see, from http://www.php.net/manual/en/language.operators.php, . has higher precedence than ?:, so this:

> echo "string1 ".empty($var)?0:$var." string2";

resolves to:

  echo ("string1 ".empty($var))?0:($var." string2");

which seems like it'll echo "0" to me...

The answer, as you rightly show, is to use parentheses to override the precedence.

On your other error messages:

> echo 'string1 '.empty($var)?0.' string2';

is just plain wrong since the operator is ?: and must have all parts present; but I guess it also fails because the parser is reading "0." as a floating number and objecting to the immediately following string quote.   This would also apply to:

> echo 'string1 '.0.' string2';

Again, the solution would be to wite it in a way that is not ambiguous, e.g.:

  echo 'string1 ' . 0 . ' string2';

Cheers!

Mike
 [2002-07-30 11:45 UTC] rasmus@php.net 
No bug here.  It is consistent with the documented operator precedence.
 
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