Mike,
So, in PHP, when a string is converted to a number to compare with the other
decimal input, the compiler doesn't look at the ascii set table *at all*?
Instead, it simply convert the string to 0?
cheers,
feng
----- Original Message -----
From: "Ford, Mike [LSS]" <[EMAIL PROTECTED]>
To: "'Wang Feng'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
Sent: Monday, October 20, 2003 10:18 PM
Subject: RE: [PHP] sorting
> On 18 October 2003 10:10, Wang Feng wrote:
>
> > I can't uderstand why the number 18 is stored in the $third
> > rather than
> > $first. I tried to change the 18 to "18", that is, change it
> > from a decimal
> > number to a string and by that way, "18" is stored in the $first,
> > which is what I expected. But why doesn't 18 work?
> >
> > My understanding is that the compiler checks the ascii set
> > when it deals
> > with sorting. So, why the number 18 is *greater* than string "blue"
> > and "large" in the ascii?
>
> This is all to do with how PHP handles comparison of different types to
each other.
>
> When that sort is run on
>
> array("large", "blue", 18.00)
>
> the comparison of "large" to "blue" is fine, because both are strings so
there's no type conversion involved. However, the comparison of 18.00, a
number, to either "blue" or "large", both strings, necessarily involves a
type conversion, and the rules PHP uses says that when comparing a number
with a string, the string should be converted to a number and teh comparison
performed using the two numbers -- and both "blue" and "large", when
converted to a number, are represented by 0, which sorts before 18, so
bingo!
>
> Now, if you make the array into
>
> array("large", "blue", "18.00")
>
> then all the comparisons are string-ti-string, so there are no type
conversions involved, so your sort proceeds exactly how you expect.
>
> If you wish to sort an array containing values of more than one type, then
you must either be fully aware of these type-conversion rules and accept the
slightly odd results they will sometimes give you, or use one of the
optional sort flags -- SORT_STRING or SORT_NUMERIC -- to force a more
uniform comparison. But don't forget that if you use SORT_STRING and have
an array containing numbers, you will get a textual sort of those numbers --
for example: 1, 5, 33, 297 would sort as "1", "297", "33", "5"!!
>
> Cheers!
>
> Mike
>
> ---------------------------------------------------------------------
> Mike Ford, Electronic Information Services Adviser,
> Learning Support Services, Learning & Information Services,
> JG125, James Graham Building, Leeds Metropolitan University,
> Beckett Park, LEEDS, LS6 3QS, United Kingdom
> Email: [EMAIL PROTECTED]
> Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211
--
PHP General Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php
