Edit report at http://bugs.php.net/bug.php?id=38437&edit=1
ID: 38437 Comment by: salsi at icosaedro dot it Reported by: zizka at seznam dot cz Summary: substr() - slightly change its contract Status: Open Type: Feature/Change Request Package: Feature/Change Request PHP Version: 5.1.4 New Comment: The manual states that "If length is given and is 0, FALSE or NULL an empty string will be returned.". This is not true, as substring($s, $start, $length) seems to behave in a very unpredictable way with NULL string, empty string and at the string boundaries when $length==0: var_dump( substr("a", 0, 0) ); # => "", ok var_dump( substr("a", 1, 0) ); # => FALSE rather than "" var_dump( substr("", 0, 0) ); # => FALSE rather than "" var_dump( substr(NULL, 0, 0) ); # => FALSE rather than "" In my opinion, substr() should always return a string, possibly empty, of length $length bytes provided that 0 <= $start and $start + $length <= strlen($s). And then an empty string should be returned when $length==0. If $start is negative, the value $start = strlen($s) - $start should be considered and the algorithm above applied. The NULL value should be considered as the empty string "" as in PHP tradition. Previous Comments: ------------------------------------------------------------------------ [2006-08-12 20:34:14] zizka at seznam dot cz Description: ------------ string substr ( string string, int start [, int length] ) Currently: If string is less than *or equal* to start characters long, FALSE will be returned. I suggest: If string is less than start characters long, FALSE will be returned. The latter is more "ideologically clean". See the behavior of analogical methods in Java, JavaScript, C, etc. E.g. I did some simple parser, where the string of the form $<anything> is expected. I wanted to get <anything>, so I did: if($s !== '' && $s[0] == '$') $s2 = substr($s, 1); Then, behaved by Java's String.substring(), I wrote: if($s2 === '') // Replace $s2 with some default value; After several minutes of searching for the bug, I noticed the fact mentioned above. Reproduce code: --------------- substr("Ahoj", 4); Expected result: ---------------- An empty string. Actual result: -------------- FALSE. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=38437&edit=1