Autodecrementing variables

[theoneweasel77]

I know that if you have a variable $var = "c", you can say $var++ and $var now equals d. Can you autodecrement $var? (I used $var-- and it didn't change the value).

 

[sleipnir214]

The "--" operator should have done it.


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[theoneweasel77]

It didn't. Output is at

http://www.thespaz.net/games/board_display.php

and source follows

<?
	$var = "c";
	$i = 3;
	print $var;
	print "<br>";
	print $i;
	print "<br>";
	$var--;
	$i--;
	print $var;
	print "<br>";
	print $i;
?>

If you need to see the php.ini file, it's at

http://www.thespaz.net/PHPtesting/phpinfo.php

 

[sleipnir214]

Aha.

This is by design. The online manual entry for Incrementing/Decrementing Operators includes the text:

Note that character variables can be incremented but not decremented.


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[theoneweasel77]

so, if I made it a string, could I get away with it? (example $var = "foo" $var-- would give me "fon")

 

[theoneweasel77]

that didn't work either... What is meant by "character variables"?

 

[sleipnir214]

No, you will get "foo".

Again:

Note that character variables can be incremented but not decremented.


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[theoneweasel77]

what is a "character variable"?

 

[sleipnir214]

A variable that contains a character value. As opposed to integer, float, array, object, or boolean values.


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[theoneweasel77]

In case anyone wondered, there is a way around this with the chr function

 

[sleipnir214]

You could probably do something using chr(). But first, you have do define what the decrement means, particularly at the limits of its range.

If $var = 'a', what will the value in $var be after $var-- ?


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[flugh]

How about:
[tt]
$var = ord($var) - 1;
[/tt]

http://us2.php.net/manual/en/function.ord.php

Wrap some logic around it to account for the a-z range as needed. Get all your ascii codes in one place here.

----
JBR