Re: strcmp() versus ==

On Mon, 16 Mar 2009 17:06:35 -0500, nospam@mckenzies.net (Shawn McKenzie) wrote: >Shawn McKenzie wrote: >> Paul M Foster wrote: >>> I had never completely read over the rules with regard to comparisons in >>> PHP, and was recently alarmed to find that $str1 == $str2 might not >>> compare the way I thought they would. Is it common practice among PHP >>> coders to use strcmp() instead of == in making string comparisons? Or am >>> I missing/misreading something? >>> >>> Paul >>> >> >> I would use $str1 === $str2 if you want to make sure they are both >> strings and both the same value. >> >> Since PHP is loosely typed, "0" == 0 is true however "0" === 0 is >> false. >> > >If you want to force a string comparison you can also use: > >(string)$str1 == (string)$str2 Recently there was some discussion about inexplicable results from sorting alphanumeric strings. Inspired by your suggestion I filled in an array with random 4 character alphanumeric strings, and then wrote a simple bubblesort. I made two copies of the array, and sorted one using a simple comparison, and the other using the above comparison. The initial values of the array were : $aa = array ('ASDF','01A3','0A13',1,'00A3','ZZZZ','001A','0000','7205','00Z0'); (There are no letter 'O's in this), And the results I got were: Tb2_38: Original Raw comp String Comp ASDF 0000 0000 01A3 00A3 001A 0A13 01A3 00A3 1 0A13 00Z0 00A3 ASDF 01A3 ZZZZ ZZZZ 0A13 001A 1 1 0000 001A 7205 7205 00Z0 ASDF 00Z0 7205 ZZZZ Apart from the out of place '1', apparently treated as '1000', which I threw in out of curiosity, the string comparison gave the expected results, but I cannot see the logic of the raw comparison. Can anybody explain these results? Clancy If anyone is suspicious the actual code I used was: $aa = array ('ASDF','01A3','0A13',1,'00A3','ZZZZ','001A','0000','7205','00Z0'); $k = count ($aa); $bb = $aa; $cc = $aa; while ($k > 1) { $i = 0; $j = 1; while ($j < $k) { if ($cc[$i] > $cc[$j]) { $t = $cc[$i]; $cc[$i] = $cc[$j]; $cc[$j] = $t; } ++$i; ++$j; } --$k; } $k = count ($aa); while ($k > 1) { $i = 0; $j = 1; while ($j < $k) { if ((string)$bb[$i] > (string)$bb[$j]) { $t = $bb[$i]; $bb[$i] = $bb[$j]; $bb[$j] = $t; } ++$i; ++$j; } --$k; } echo '<p>Tb2_38: Original&nbsp;&nbsp;&nbsp;Raw comp &nbsp;&nbsp;String Comp</p>'; $i = 0; $k = count ($aa); while ($i < $k) { echo '<p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; '.$aa[$i]. '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'.$cc[$i]. '&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;'.$bb[$i].'</p>'; ++$i; }