substr($s,$n,$m) is supposed to always return a string (at least if $s
is a string and $n and $m are integers).

However:

   is_string(substr($s,strlen($s),$m)) 

returns false, so substr did not return a string.

Example:
echo is_string("")."<BR>\n";
echo "substr(\"A\",0,1):".is_string(substr("A",0,1))."<BR>\n";
echo "substr(\"A\",0,0):".is_string(substr("A",0,0))."<BR>\n";
echo "substr(\"A\",1,1):".is_string(substr("A",1,1))."<BR>\n";
echo "substr(\"A\",1,0):".is_string(substr("A",1,0))."<BR>\n";

Please try using this CVS snapshot:

  http://snaps.php.net/php4-latest.tar.gz
 
For Windows:
 
  http://snaps.php.net/win32/php4-win32-latest.zip

jan@dahlia ~> php bug_20695.php
1<BR>
substr("A",0,1):1<BR>
substr("A",0,0):1<BR>
substr("A",1,1):<BR>
substr("A",1,0):<BR>
jan@dahlia ~> php -v
PHP 4.4.0-dev (cli)

works fine here

No feedback was provided. The bug is being suspended because
we assume that you are no longer experiencing the problem.
If this is not the case and you are able to provide the
information that was requested earlier, please do so and
change the status of the bug back to "Open". Thank you.

Hi Jan,

thanks for you reply! I have tried the snapshot
(for Windows) that you pointed me to. The program
works as you say - which IMHO is a bug.

The output is - as you mention:

1<BR>
substr("A",0,1):1<BR>
substr("A",0,0):1<BR>
substr("A",1,1):<BR>
substr("A",1,0):<BR>

This means that substr("A",1,1) and substr("A",1,0) are both
not strings. Therefore substr does _not_ always return a string.
If this is considered correct, then it should be mentioned in
the documentation. 

Personally, I would prefer this to be considered
incorrect: I would prefer substr($s,$n,$m) to always return a string, 
at least if $s is a string and $n and $m are integers.

Please either improve the documentation or make substr($s,$n,$m) 
always return a string (at least if $s is a string and $n and $m are integers).

Thanks for putting this PHP together. It is a great means to produce results quickly!

Cheers,
	Raimund

This script shows clearly what happens:

<?php

var_dump(substr("A",0,1));
var_dump(substr("A",0,0));
var_dump(substr("A",1,1));
var_dump(substr("A",1,0));

?>

Output:

string(1) "A"
string(0) ""
bool(false)
bool(false)

And this is quite correct and expected behaviour.
Documentation though should mention that invalid start position and length will make it return FALSE.

..and that's what the docs say too.. :)

What if I make the following call to substr ?
var_dump(substr('', 0));

The documentation says "If string is less than start characters long, FALSE will be returned".
That can be very ambiguous because start is 0 and the length of the string is 0 (not less).
Another problem: mb_substr does not work like this. If you overload the functions and make the same call as above it will return an empty string.

Thanks in advance.