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Request #40531 mb_substr optional parameters
Submitted: 2007-02-18 08:15 UTC Modified: 2012-08-01 02:00 UTC
Avg. Score:4.5 ± 0.5
Reproduced:4 of 4 (100.0%)
Same Version:4 (100.0%)
Same OS:2 (50.0%)
From: emwebdev at hotmail dot com Assigned:
Status: Wont fix Package: mbstring related
PHP Version: 5.2.1 OS: Windows XP
Private report: No CVE-ID:
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 [2007-02-18 08:15 UTC] emwebdev at hotmail dot com
Hi there

I'm not sure if the following is intended functionality or a bug, but I've tried many forums etc. and been unable to get an answer.

When you use mb_substr() and omit the third argument (length), the function returns all characters from the start index to the end of the string.

This is fine unless you want to specify the character encoding explicitly as the fourth argument. This forces you to supply the length argument also.

It would seem logical that passing null for the length argument would make mb_substr() behave the same as if it had been omitted, but this is not the case.

Passing null as the length argument to mb_substr() (or substr() itself for that matter) will produce an empty string every time.

This means that to achieve the same functionality displayed when the length argument is omitted, you have to calculate the remaining string length yourself which is no doubt much less efficient.

Thanks for your time,


Reproduce code:
var_dump(substr('foobar', 3));
var_dump(substr('foobar', 3, null));

Expected result:
'bar' (length=3)
'bar' (length=3)

Actual result:
'bar' (length=3)
'' (length=0)


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 [2007-02-18 08:18 UTC] emwebdev at hotmail dot com
Apologies, reproduce code should be as follows:

var_dump(mb_substr('foobar', 3));
var_dump(mb_substr('foobar', 3, null));

Expected and actual results are the same.

 [2011-02-21 21:12 UTC]
-Package: Feature/Change Request +Package: mbstring related
 [2012-07-31 11:11 UTC] spam02 at live dot com
seems null = not empty in mb_substr()...
$text = 'test';

mb_substr($text,-1);  //result t
mb_substr($text,-1,null) //result '' expected t
substr($text,-1); //result t
substr($text,-1, null) //result '' expected t
php version 5.3.3-7+squeeze13
 [2012-07-31 14:33 UTC]
I am not sure about this,  fix will be easy, but bc break..
 [2012-08-01 02:00 UTC]
-Status: Open +Status: Wont fix
 [2012-08-01 02:00 UTC]
Documented behaviour, same reasoning as bug #62703.
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