get value of checkbox and perform computation

Question

I have 3 checkboxes:

<label><input type="checkbox">100%</label>
<label><input type="checkbox">50%</label>
<label><input type="checkbox">25%</label>

and one textbox1 that have fix value

<?php 
    $sampleValue= "200.35"
?>
<input type="text" class="form-control" id="sampleOfsample"  readonly="readonly" value="<?php echo $sampleValue ?>" >

If the checkbox check one it will get the % the value of $sampleValue and it will echo the amount at the same textbox.

How can I achieve this?

Thanks...

`value = "` => `value = ""/>` you haven't close out of `php` and missing a double quote to close the value attribute. — NewToJS, Nov 20 '17 at 07:16
What if one selects more than one checkbox at a time?? Use radiobutton instead — Yash Parekh, Nov 20 '17 at 07:20
you mean to say anyone one of three check box one is checked then you want to show text box value otherwise none right? — Ritesh Khatri, Nov 20 '17 at 07:20
yes sir, if any check box is check it will perform computation and i will display the value in the same text box @Rits — gene ian Gutierrez, Nov 20 '17 at 07:26
what computation?? and above two code snippet is in the same file? — Ritesh Khatri, Nov 20 '17 at 07:30
if the user select one checkbox it will compute the % of $sampleValue = "200.35". @Rits — gene ian Gutierrez, Nov 20 '17 at 07:36
@geneianGutierrez If you want to limit the client from only being able to select one option with a `checkbox` you might find [**one of my previous answers**](https://stackoverflow.com/questions/42989096/how-can-i-make-the-radio-boxes-in-html-look-like-checkboxes-and-make-them-have-x/42989382#42989382) helpful. — NewToJS, Nov 20 '17 at 08:02

score 3 · Answer 1 · answered Nov 20 '17 at 07:29

I think you use only PHP without JavaScript and need to transfer data from one file to another. I assume you have form like this:

<form method="POST" action="fileName.php">
    <label><input type="checkbox" name='checkBoxOne'>100%</label>
    <label><input type="checkbox" name='checkBoxTwo'>50%</label>
    <label><input type="checkbox" name='checkBoxThree'>25%</label>
    <input type="Submit" value ="Submit"/>
</form>

Now what happens on the back-end side (fileName.php)

$checkBoxOne = $_POST["checkBoxOne"]
$checkBoxTwo = $_POST["checkBoxTwo"]
$checkBoxThree = $_POST["checkBoxThree"]

You check which one is filled and input into field`s value like:

<input type="text" class="form-control" id="sampleOfsample"  readonly="readonly" value="<?php echo $sampleValue ?>" >

Also, I would suggest to use "Select" element and not checkBox, because it will always send "one" value and you won't have to check each checkbox values.

get value of checkbox and perform computation

1 Answers1