Help with PHP and associative arrays

Question

I have to do a simple calculator in php based on user's input and choice from select field, something like this:

<?php
$a = $_GET['a'];
$b = $_GET['b'];

$array = array( "option1" => 0.1,
                    "option2" => 0.15,
                    "option3" => 0.3,
                    "option4" => 3,
                    "option5" => 3,
                    "option6" => 16,
                    "option7" => 16,
                    "option8" => 16
                    );

echo "<form action='calc.php' method='get'>";
echo "<input type='text' name='a' value='".$a."'> of ";
echo "<select name='b'>";
foreach ($array as $k => $v) {
    echo "<option value='".$v."'>".$k."</option>";
}
echo "</select> ";
echo "<input type='submit' value='='> ";

$total_volume = $a * $b;

echo $total_volume;

echo "</form>";
?>

Well, for now everything works fine, but the idea is that after user submits form, the page reloads with sent amount in input field and selected option which user actually selected...

First thing is easy: I just put value="a" in my input field, but I'm not sure how to make a selected option in <select> field???

I started with this:

foreach ($array as $k => $v) {
        echo "<option value='".$v."'";
        if ($b == $v) {
            echo " selected ";
        }
        echo ">".$k."</option>";
    }

...but this is obviously not working as expected... Please help me with this easy one :)

Thanks!

The foreach code you wrote should be fine. You might want to use echo ' selected="selected"'; instead of the non-XHTML-compliant echo ' selected'; though — phsource
– phsource, Commented Jun 2, 2010 at 22:11

jeroen · Accepted Answer · 2010-06-02 22:43:58Z

2

You need to echo something like 'selected="selected"'. The rest of the code seems fine to me.

On second thought there is something structurally wrong as multiple options return the same value, making it impossible to select the right one after submitting the form.

You will need to send $k as the value in the select in your loop and for your calculations you just use $array[$b] instead of $b.

<?php
$a = $_GET['a'];
$b = $_GET['b'];

$array = array( "option1" => 0.1,
                    "option2" => 0.15,
                    "option3" => 0.3,
                    "option4" => 3,
                    "option5" => 3,
                    "option6" => 16,
                    "option7" => 16,
                    "option8" => 16
                    );

echo "<form action='calc.php' method='get'>";
echo "<input type='text' name='a' value='".$a."'> of ";
echo "<select name='b'>";
foreach ($array as $k => $v) {
        echo "<option value='".$k."'";
        if ($b == $k) {
            echo ' selected="selected"';
        }
        echo ">".$k."</option>";     // or $v if you want to show the number
}
echo "</select> ";
echo "<input type='submit' value='='> ";

$total_volume = $a * $array[$b];

echo $total_volume;

echo "</form>";
?>

edited Jun 2, 2010 at 22:43

answered Jun 2, 2010 at 22:12

jeroen

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7 Comments

streetparade Over a year ago

I agree structured code is very important. Bad code is a lack of proffesionality in my opinion

errata Over a year ago

I think that your second thought is the closest to my solution :) I should definitely send string of selected option with my form, right?

jeroen Over a year ago

@errata, yes if you want to distinguish what option was selected, the values need to be unique, like option1 ... option8

errata Over a year ago

Yes, it occurred to me also :) But how could I send $k with form in my situation so I could fetch it with $_GET at the end?

jeroen Over a year ago

@errata, I´ve made two small modifications to your code, see above.

|

dnagirl · Accepted Answer · 2010-06-02 22:13:51Z

2

Try this:

foreach ($array as $k => $v) {
   $selected= ($b == $v) ? 'selected="selected"' : '';
   echo "<option value='$v' $selected>$k</option>\n";
}

answered Jun 2, 2010 at 22:13

dnagirl

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Comments

streetparade · Accepted Answer · 2010-06-02 22:21:45Z

-1

You have to catch the data in $_GET. Try

foreach ($_GET as $k => $v) {
        echo "<option value='".$v."'";
        if ($b == $v) {
            echo " selected ";
        }
        echo ">".$k."</option>";
    }

EDIT:

On my Computer it worked here is the dump of GET

        <form action='' method='get'>
    <input type='text' name='a' value='121'> of <select name='b'>
<option value='0.1'>option1</option>
<option value='0.15'>option2</option>
<option value='0.3'>option3</option>
<option value='3'>option4</option>
<option value='3'>option5</option><option value='16'>option6</option><option value='16'>option7</option><option value='16'>option8</option></select> <input type='submit' value='='> 363
    </form>

The Url

http://localhost/test.php?a=121&b=3

And parameters

a 121 b 3

edited Jun 2, 2010 at 22:21

answered Jun 2, 2010 at 22:15

streetparade

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1 Comment

jeroen Over a year ago

Sorry, but this is just completely wrong. Submitting 2 values will get you 2 options with your code with values 121 and 3 and text a and b.

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