Doc #73132 [Opn->Nab]: mb_substr() doesn't always return a string

Edit report at https://bugs.php.net/bug.php?id=73132&edit=1 ID: 73132 Updated by: cmb@php.net Reported by: greg dot bor at franchisedirect dot com Summary: mb_substr() doesn't always return a string -Status: Open +Status: Not a bug Type: Documentation Problem Package: Documentation problem Operating System: irrelevant PHP Version: Irrelevant -Assigned To: +Assigned To: cmb Block user comment: N Private report: N New Comment: The NULL return value is not special to mb_substr(), as the documentation about internal functions already states[1]: | If the parameters given to a function are not what it expects, | such as passing an array where a string is expected, the return | value of the function is undefined. In this case it will likely | return NULL but this is just a convention, and cannot be relied | upon. [1] <http://php.net/manual/en/functions.internal.php> Previous Comments: ------------------------------------------------------------------------ [2016-09-20 18:04:58] greg dot bor at franchisedirect dot com Description: ------------ --- From manual page: http://www.php.net/function.mb-substr --- "Return Values" says this returns a string, which is true for most cases but not true for at least one edge case: var_dump(mb_substr(array(), 0, 1)); returns NULL in PHP 5.3+ (but returns "A" before PHP 5.3). I haven't checked the PHP source, I guess these it can be determined when exactly does mb_substr return NULL. Test results with https://3v4l.org/CuDLX: Output for 5.3.0 - 5.4.45, 5.5.0 - 5.5.34, 5.5.35 - 5.6.26, hhvm-3.10.0 - 3.14.4, 7.0.0 - 7.1.0RC2 ` Warning: mb_substr() expects parameter 1 to be string, array given in /in/CuDLX on line 3 NULL ` Output for 4.3.0 - 5.2.17 ` Notice: Array to string conversion in /in/CuDLX on line 3 string(1) "A" ` Test script: --------------- var_dump(mb_substr(array(), 0, 1)); Expected result: ---------------- The documentation should define when does mb_substr returns NULL. Actual result: -------------- The documentation suggests mb_substr always returns a string. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=73132&edit=1