change specific characters within a 'string' via form

gjwalsh

Assume a field labeled 'qr' in a data base, defined as character(6), and with an existing value of '#aaaaa' in local variable $qr.

Assume also a form which, upon submission, returns this array:
([q{1}] => y [q{3}] => y [q{5}] => n [send] => SAVEIT)

I need to end up with $qr = '#yayan'.

To do this I tried:
for($i=1; $i < 7; $i++)
if (isset($POST["q{$i}"])) $qr{'$i"} = $POST["q{$i}"];

... which results in no logged errors, but the value of $qr is unchanged.

What kindergarten level error have I humiliated myself with here?

bradgrafelman

Can you change the form to submit an array instead? Example:

#1: <input type="text" name="q[1]">
#2: <input type="text" name="q[2]">
...

If so, that'd make your life easier, and you could simply do:

$qr = '#aaaaa';

foreach($_POST['q'] as $pos => $val)
    $qr[$pos] = $val;

gwalsh

Thanks for getting back to me. MUCH appreciated.

Actually, the form responses are collected from radio buttons like so:

The field in the data base table is fully initialized when the record is created.
The form in effect 'edits' the string to reflect the answers.

So ..... it would seem that I should replace the for loop with the foreach script you suggested which then gets the response into the correct 'pew'.

Looks good to me .... I'll give it a try.

Thanks for the suggestion.

gwalsh

Nope .... that has no effect either.

Maybe I have to take the character string from the data base and convert it into an associative array first (and then back again, of course. Seems terribly clumsy.

This project is an involved conversion of psychometrics from C and i-sam. It was clean, simple, and efficient. But converting to PHP and postgresql has been anything but.

bradgrafelman

Do you have no choice as to how the radio buttons are generated? Can you not change the {}'s to []'s in the HTML code?

If not, you could replace the foreach() with the following, although with one caveat:

for($i = 1; isset($_POST['q{' . $i . '}']); $i++)
    $qr[$i] = $_POST['q{' . $i . '}'];

Caveat: If there is any break in the sequence, the for() loop will stop and the remaining 'q' elements submitted won't be processed. In your example above, I only saw the numbers 1, 3, and 5 appear... does this mean that only odd-number q values are submitted? If so, then the increment on the count would need to be modified to $i += 2 so that the for() loop only works with odd numbers. Otherwise, your best solution is to change the {}'s to []'s in the HTML so that you can work with arrays instead.

gwalsh

You bet! I changed the {} syntax to [] throughout and everything fell into place.

That came about from "Beginning PHP and PostgreSQL 8", page 191/192, where 'Complex (Curly) Offset Syntax' is supposed to remove the ambiguity of the square brackets which have been deprecated when working with strings.

Perhaps I misunderstood that, but we are back to the deprecated [] syntax, and I'll gladly put up with the ambiguity assumption in exchange for a functioning script.

My sincerest thanks for your having taken the time and trouble to help me trouble shoot this.

bradgrafelman

The ambiguity between [] and {} lies in PHP, where it used to be that to access certain positions in a string you would use the curly braces, i.e. $string{3} to get the 4th character, and that using brackets was deprecated.

Now the powers that be have gone back on their decision and the reverse is true now. Personally, I agree that the current method - using brackets - is more suiting. The brackets, in PHP, are associated with arrays... which is actually what a string is, an array of characters strung together. Reminds me of C++ and NTCA's.

gwalsh wrote:
My sincerest thanks for your having taken the time and trouble to help me trouble shoot this.

My pleasure - glad we got it sorted. Don't forget to mark this thread resolved (using the link under Thread Tools at the top).