really confused about converting strings to variables

Davidc316

I've spent two days on working on this problem and now the white flag is up and I have to declare that I'm totally stuck. I think it's quite complicated so I'll try to explain it as best as I can and just hope that somebody out there can help...

I have a form. A very big form with lots of textfields. It's an application form for some stuff.
There is every chance that the fields on this big form could change at any time (so next week I might need to add more textfields, delete some textfields or edit them in some way or another).
Several pages on the website will be displaying this form in a range of credes and colours.
I have therefore created a MySQL table that contains all the information necessary to dynamically draw the form. So, if somebody wants to change the form in the future, all I have to do is add a row to a MySQL table.

/////////////////////////////////////////////////////////////////////
//NO PROBLEMS SO FAR AND EVERYTHING IS COOL//
/////////////////////////////////////////////////////////////////////

When the form is FIRST presented to the user some of the variables will be automatically filled in. (it does this by remembering who the user is and printing some of their details onto the form when they arrive at the form page).
However, if the user submits a form that has not been properly filled out then the page displays a list of all the errors that the person made (it does this by creating an array of all the errors and then extracting them).
...and then (when there has been a form submission error) the form is included onto the page, only this time each of the textfields will display all of the variables that the user has previously posted.

/////////////////////////////////////////////////////////
//*THIS IS WHERE THE PROBLEMS BEGIN**//
////////////////////////////////////////////////////////

Because each row of the row is dynamically generated (from a table), the code for generating each textfield will look something like this...

<tr><td><b>
<?php
print $friendly_name; 
?> : </td>
<td><input type="text" name="<?php print $var_name; ?>" maxlength="60" size="30" value="<?php
$var="$";
$var.=$var_name;
print $var;
?>"></td></tr>

...this leads to problems, because when I view the page, the values that get displayed in the textfield are things like "$name", instead of "David".

I'm totally stuck and would be mega grateful if anyone could offer any pointers.

My general vibe is humble.

Roger_Ramjet

Well, what do you expect? You set $var to a string and then concatenate another string to it so all you've ever got is a string.

Now what you want to do is use Variable Variables and the best thing to do is go read the manual so you know how to do it from now on.

Plasma

<td><input type="text" name="<?php print $var_name; ?>" maxlength="60" size="30" value="<?php
$var="$";
$var.=$var_name;
print $var;
?>"></td></tr>

What are you doing with the value bit?

Try:

<td><input type="text" name="<?= htmlentities($var_name) ?>" maxlength="60" size="30" value="<?= htmlentities($_REQUEST[$var_name]) ?>"></td></tr>

First off, we htmlentities() the tag names, incase they contain a quote/special character.

Finally, the 'value' of this particular input box is set to what the form posted/get'd to itself.

$REQUEST contains the values from both GET and POST (since I dont know which one you are using, ill just go with REQUEST).

<?=$test?>

Is shorthand for:

<?php echo $test ?>

<?= (<? equals) means 'print/echo this out' - without having to write the print/echo statement.

The above code changes should work fine for your app.

Davidc316

Plasma- many thanks for that. I tried it out, but I'm afraid it simply doesn't work. I really appreciate your help.

Roger Ramjet- when I created this post, I wanted to describe my problem in the most simple and clear way I could. Having worked on the problem for two days I am well aware of the fact that what I've posted above would generate a string and not a variable. I spent a full day reading up on and experimenting with variable variables before creating this post.

I realise it's very fashionable in these parts to assume that people haven't bothered to look at the manual and tell them to go read it (which is kind of a ridiculous request to make in the first place considering the massive, ever expanding size and complexity of the PHP manual), however, I can assure you that I have spent several hours labouring over the manual, this forum and indeed the net in general. It seems to me that the manual is not addressing my problem or I have failed to understand the manual. Either way, telling me to go and read the manual doesn't really help.

Anyway, thanks for the link and for the help.

Unfortunately, for me, this thread is not resolved.

Plasma

Are the values of $var_name correct? Do they change between page loads?

Also I assume you are POST/GETing the data back to the form itself, otherwise it wont since you never give the form its data again.

Davidc316

Yes Plasma (and thanks for your continued help). The values of $var_name are indeed correct. Before I give up and admit defeat, I'm gonna try to clarify the current state of play (for myself, more than anything) one last time...

So, in its most simple form what I have is the following:

<?php
$name="David";
$address="some street in the UK";
$age="30 years young";
$height="shorter than average";
$eyecolour="blue";
//...and lots more variable declarations

$var_name="name";
//Now, I need to somehow print/echo the value of the variable that is called "name"...
?>

This one is killing me.

Megahertza

David, question? are you trying to create a variable and name the variable dynamically.

Roger_Ramjet

Hey, don't cop-the-hump. The reason I said you should go and read the manual is because this is difficult to get your head around and I thought the manual explained it better than I ever could. And yes lots of newbies don't even know where the manual is, or how to search it if they do; so I did the search and gave you the link. If I wanted to be rude I'd have just said RTFM (read the effing manual).

So, as I understand it, you have a presentation script that you want to work with dynamic and indeterminate data fields. My guess is that actually the data could be submitted from various forms written by various people, and possibly posted form various domains. So you have no certainty over what will be posted to your script, either the number or the names of the vars.

2 ways to handle that.

POST submits an array and you can just use the array handling constructs like foreach


foreach ($_POST as $key=>$val) {
   echo '<td><input type="text" name="' . $key . '" maxlength="60" size="30" value="' . $val . '" /></td>';
}

That will output all fields posted no matter how many or what their names. You could add IFs or a SWITCH to eliminate unwanted vars like $_POST['submit'].

Now, the way you were approaching this will not work. Using variable variables you get the contents of $var_name as the name of a new var

// if $var_name holds the value 'David' then
$$var = $var_name;
// will give you a var named $David, and it will be empty
echo ${$var};
// will output nothing because you have not yet given it a value

What yu are tryuing to do is to alias $var_name so that you can use standard code for variable content. The foreach construct is the best way I know to handle that. There are various other array handling functions that can achieve the same. but they are less efficient.

Davidc316

Am I trying to create a variable and name it dynamically?

I'm so confused now that I'm not even sure.

The variable of (let's say) $name has already been passed to the page. I am trying find a way of saying to php "Hey PHP, please print whatever values you have for the variable that is $name".

The part that needs to be dynamic here is the "Hey PHP, please print whatever values you have..." bit. The reason it needs to be dynamic is because I won't always be interested in the variable that is called $name. There will be occassions where I'm interested in other variables (such as $age, for instance).

The good news is that my script does a wonderful job of telling me what variable I'm interested in. It does this by creating a variable called $var_name and gives it values like "name", "age"...and so on. As I said in my original post, the problems begin when I try to then print the value that has been reported for the variable of (in this example) $name.

Davidc316

Ok Ramjet. I've read what you've said and have taken it on board. Thanks.

What was originally an idea for a cute dynamic feature is starting to turn into a never ending crusade. I really appreciate your help and ideas, but right now I've entrenched myself so deep in this variable variables business that the idea of changing course and exploring another somewhat unfamiliar avenue (like passing arrays) seems beyong my capabilities at this stage.

For the moment, I think I'll just march on and accept the fact that if the form fields change then I'll need to tweak the script(s). Sod it.

One thing that the thread has confirmed in my mind, on a slightly more positive note, is that there is a definite need for someone out there to build a dynamic form generation and processing script for PHP. I don't know about you guys, but I spend about 30% of my waking hours writing scripts that generate and process forms.

When I have more time, I would like to embark on a mission to write some kind of script that allows users to easily and quickly create and process PHP/MySQL driven forms. That would be cool.

PS- actually, upon a second glance I realise that your array method does seem pretty good. I think I'll give it a go.

PPS- I've just visited Hotscripts and see there are 277 form wizards. Perhaps my idea isn't as ground breaking as I first thought.

Roger_Ramjet

Well, dave, I am used to processing indeterminate data fileds in VB, we use the foreach construct there too; only they are 'collections' of form controls not arrays of values. In VB you also have the advantage of being able to test for the type of control/element and ignoring types yu don't need to process.

To do this in php, I pass an array of field names to the script along with the form data. You then just do an array comparison before processing each element


$use = array('name', 'address', 'age', 'height');

foreach ($_POST as $key=>$val) {
    if (in_array($key, $use)) {
         echo '<td><input type="text" name="' . $key . '" maxlength="60" size="30" value="' . $val . '" /></td>';
   }
}

That is about as dynamic as you can ever need to get:
process untold vars of untold names with untold contents, and use a list to determine how to process each one (because of course it could be an IF/ELSE, or multiple arrays of field names, or whatever other conditions you want and need.