ID: 41384
Updated by: [EMAIL PROTECTED]
Reported By: hg at ecs dot soton dot ac dot uk
-Status: Open
+Status: Closed
Bug Type: Documentation problem
PHP Version: Irrelevant
New Comment:
This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.
Thank you for the report, and for helping us make our documentation
better.
"var_dump("1" == "1e0");" added to the example.
Previous Comments:
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[2007-05-13 12:12:45] hg at ecs dot soton dot ac dot uk
Description:
------------
On http://uk.php.net/manual/en/language.operators.comparison.php
My suggestion is that, at least, the start of the example should be
changed to:
<?php
var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
var_dump("1" === "01"); // 1 !== 1 -> false
var_dump("0000e002073" == "0e2857"); // 0 == 0 -> true
var_dump("0000e002073" === "0e2857"); // 0 !== 0 -> false
The explanation is in the note I have submitted to the page;
Warning, string comparison may be even stranger than you thought:
<?php
$a = "0e2";
$b = "0e3";
if ($a == $b) print '$a == $b'."\n"; // True
if ($a === $b) print '$a === $b'."\n"; // False
if ("000e002073" == "0e2857") print '"000e002073" ==
"0e2857"'."\n"; // True
?>
outputs
$a == $b
"000e002073" == "0e2857"
According to Table 15.4, since $a and $b are of the same type, it
might have been expected that == and === gave the same result? Not
necessarily.
The clue is in the text below the table:
"If you compare two numerical strings, they are compared as integers."
Since these strings are numerical strings (in fact floats, if you
hadn't worked it out yet), they are compared as integers.
This is the behaviour we know and love about php, and I have no
problem with it. I do have a problem that == and === give different
answers for objects when "they are of the same type."
I think that Table 15.4 gives no inkling of this.
Table 15.5 might have made the situation clearer, but makes no
distinction between == and ===.
Of course, to be really safe, we should have been using strcmp() in
any case, but it seems to be quite common that people use == for
strings, so it should be pointed out.
I am suggesting (by other mechanism) a change to the page, but in the
meantime (or if it is rejected) this note may help.
By the way, this was a real problem for me.
If you are comparing a significant number of strings which happen to
be hex, it is quite surprising to find that "000" == "0e0" whereas
"000" != "0f0".
I think I might start using things like "0e0" for username and
password on websites to see what breaks :-)
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Edit this bug report at http://bugs.php.net/?id=41384&edit=1
