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Bug #53252 Invalid type (boolean) returned by substr() when providing an empty string
Submitted: 2010-11-07 13:48 UTC Modified: 2010-11-07 20:54 UTC
From: cagret at gmail dot com Assigned: frozenfire (profile)
Status: Closed Package: Documentation problem
PHP Version: 5.3.3 OS: Linux, Windows
Private report: No CVE-ID: None
View Developer Edit
 [2010-11-07 13:48 UTC] cagret at gmail dot com 
Description:
------------
substr() returns boolean false when providing an empty string as first argument, 
but it should return an empty string "".

Example:
<?php
$s = substr('', 0, 1);
echo gettype($s);
?>

Output:
boolean (false)

There is an *error in php documentation*:
http://pl.php.net/manual/en/function.substr.php

See the example for the third argument "Length":
>> $rest = substr("abcdef", 4, -4);  // returns ""

That is not true, $rest contains FALSE and not "".

Cheers,
Cezary Tomczak

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 [2010-11-07 14:08 UTC] felipe@php.net
-Package: Strings related +Package: Documentation problem
 [2010-11-07 14:08 UTC] felipe@php.net 
The example in the documentation must be fixed.

And about your example, we have an example in the documentation that is just like your case:

var_dump(substr('a', 1)); // bool(false)

That is the expected behavior.
 [2010-11-07 16:00 UTC] frozenfire@php.net
-Status: Open +Status: Assigned -Assigned To: +Assigned To: frozenfire
 [2010-11-07 16:21 UTC] philip@php.net 
5.2.2 broke this (or fixed) but it's a BC issue. Before this time, it returned "".
 [2010-11-07 16:23 UTC] philip@php.net 
I referred to the documentation example above. Passing in an empty string always 
returned false.
 [2010-11-07 16:28 UTC] frozenfire@php.net
-Status: Assigned +Status: Closed
 [2010-11-07 16:28 UTC] frozenfire@php.net 
This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.
 [2010-11-07 16:28 UTC] philip@php.net
-Status: Closed +Status: Assigned
 [2010-11-07 16:28 UTC] philip@php.net 
Sorry, I'm being unclear this early morning.

It's $rest = substr("abcdef", 4, -4) that changed with 5.2.2, the other examples 
here have always been false. The change probably relates to PHP Bug #40754

In the very least, the substr() documentation needs a changelog entry.
 [2010-11-07 20:53 UTC] frozenfire@php.net 
Automatic comment from SVN on behalf of frozenfire
Revision: http://svn.php.net/viewvc/?view=revision&amp;revision=305175
Log: Indicated change to substr's behaviour with start positions beyond truncation positions.
Added changelog indicating this BC break. Bug #53252.
 [2010-11-07 20:54 UTC] frozenfire@php.net
-Status: Assigned +Status: Closed
 [2010-11-07 20:54 UTC] frozenfire@php.net 
This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.
 
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