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Request #71306 Remove Division by zero warning from "/" operator
Submitted: 2016-01-07 23:27 UTC Modified: 2020-01-09 11:50 UTC
Votes:6
Avg. Score:3.3 ± 1.4
Reproduced:3 of 4 (75.0%)
Same Version:2 (66.7%)
Same OS:2 (66.7%)
From: hungry dot rahly at gmail dot com Assigned: nikic (profile)
Status: Closed Package: Scripting Engine problem
PHP Version: irrelevant OS: irrelevant
Private report: No CVE-ID: None
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 [2016-01-07 23:27 UTC] hungry dot rahly at gmail dot com 
Description:
------------
It doesn't seem to throw an exception for an ACTUAL division of 0 ($var1 / $var2) and still presents as a warning

Test script:
---------------
<?php

echo PHP_VERSION."\n";
$x = 5;
$y = 0;

try {
  print "here1\n";
  $z = $x % $y;
  print "here2 - $z\n";
} catch(Error $e) {
  print "here ERROR 1 ".get_class($e)."\n";
}

try {
  print "here3\n";
  $z = $x / $y;
  print "here4 - $z\n";
} catch(Error $e) {
  print "here ERROR 2 ".get_class($e)."\n";
}

try {
  print "here5\n";
  $x = intdiv((int)$x, $y);
  print "here6 - $z\n";
} catch(Error $e) {
  print "here ERROR 3 ".get_class($e). "\n";
}


Expected result:
----------------
7.0.2
here1
here ERROR 1 DivisionByZeroError
here3
here ERROR 2 DivisionByZeroError
here5
here ERROR 3 DivisionByZeroError


Actual result:
--------------
7.0.2
here1
here ERROR 1 DivisionByZeroError
here3
PHP Warning:  Division by zero in test.php on line 17
here4 - INF
here5
here ERROR 3 DivisionByZeroError

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 [2016-01-08 00:43 UTC] bwoebi@php.net
-Status: Open +Status: Not a bug
 [2016-01-08 00:43 UTC] bwoebi@php.net 
This indeed is expected behavior; the only possible thing eventually subject to change in future is whether the warning will be removed.

But a DivisionByZeroError is definitely not suitable here as divisions by zero are handled like floating point divisions. (Yielding ±INF or NaN)
Just for integer divisions (intdiv) and modulo, there's no valid result, hence an exception is then thrown (instead of false like before).
 [2016-01-08 00:49 UTC] hungry dot rahly at gmail dot com 
Then a removal of the warning would be best, because with the warning, you are saying there is a problem, when in fact, there isn't.
 [2016-01-09 00:24 UTC] yohgaki@php.net
-Summary: DivisionByZeroError Not Throwing +Summary: Remove Division by zero warning from "/" operator -Status: Not a bug +Status: Re-Opened -Type: Bug +Type: Feature/Change Request -Package: Unknown/Other Function +Package: Scripting Engine problem -Operating System: Fedora 22/23/24 +Operating System: irrelevant -PHP Version: 7.0.2 +PHP Version: irrelevant
 [2016-01-09 00:24 UTC] yohgaki@php.net 
Make this a change request.
 [2016-03-10 13:08 UTC] axiac dot ro at gmail dot com 
It would be great to have this behaviour (who throws the exception and who doesn't) explained in the documentation of the DivisionByZeroError exception.

I submitted a patch on the documentation site that adds this information.
 [2016-03-22 20:14 UTC] ajf@php.net 
Interestingly fmod() doesn't produce a warning here, so if we got rid of the warning for `/` then we'd bring the two into alignment.
 [2020-01-09 11:50 UTC] nikic@php.net
-Status: Re-Opened +Status: Closed -Assigned To: +Assigned To: nikic
 [2020-01-09 11:50 UTC] nikic@php.net 
This has been changed to throw DivisionByZeroError in PHP 8. fdiv() is available to perform a silent division. See https://wiki.php.net/rfc/engine_warnings.
 
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