Re: strcmp() versus ==

Clancy wrote: > 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; > } Just a quick look, your original post was about comparing "strings" and as far as I know, unless you force a string comparison the < and > will do a numerical comparison, and even if I'm wrong, anything compared to your 1 will be a numerical comparison. If your just trying to sort, check out sort() and natsort(). -- Thanks! -Shawn http://www.spidean.com