I Understand the ins and outs of forms, but say for example I have the following code:
<form method="post" action="urltoserver">
<input type="checkbox" name="mycheckbox" value="1">Question</input>
</form>
Here I have set a value for the $_POST array. However, if I simply want to know if the checkbox is selected or not (ie im not bothered about the returned value), is it feasible/common practice to leave off the value attribute all together? Would it just return true/false in this case?
I'm assuming PHP since you mentioned $_POST; correct me if I'm wrong.
if a checkbox is checked (and there is no value assigned) you should (IIRC) receive an on value back (as unchecked boxes aren't sent with the request). So, if you had:
<form method="POST">
<input type="checkbox" name="foo" /> Foo
<input type="checkbox" name="bar" checked="checked"/> Bar
<input type="checkbox" name="baz" checked="checked"/> Baz
</form>
You'd see:
isset($_POST['foo']) == false
isset($_POST['bar']) == true
isset($_POST['baz']) == true
on the server-side when you went to read the check state.
the easiest thing to do though, if you're learning, is submit it to a page with the following code:
<?php
var_dump($_REQUEST);
That will show you, verbatim, what was submitted (based on the form's populated values). From there you can play with how you want to format the form to receive the values you're expecting.
Related
I've seen questions like this but none really answer this specific question. Can you include get variables in the form tag's action attribute? For example:
<form action="script.php?id=4" method="get">
<input type="text" name="thing" value="temp">
<input type="submit">
</form>`
This would theoretically result in the get request: script.php?id=4&thing=temp
I'm aware that you can simply do this:
<form action="script.php" method="get">
<input type="hidden" name="id" value="4">
<input type="text" name="thing">
<input type="submit">
</form>`
But I'm curious as to if the previous method is at all possible.
Yes you can absolutely do that! You can append any GET variables in your action attribute and just see your URL,it'll clearly show you the changes.The best use of this strategy is when you want both $_GET and $_POST variables to be there.That is,you can pass variables as GET variables by appending them to action attribute and you can simultaneously pass POST variables through the form(obviously with method attribute set as "post").
Suppose this checkbox snippet:
<input type="checkbox" value="1">Is it worth?</input>
Is there any reason to statically define the value attribute of checkboxes in HTML? What does it mean?
I hope I understand your question right.
The value attribute defines a value which is sent by a POST request (i.e. You have an HTML form submitted to a server).
Now the server gets the name (if defined) and the value.
<form method="post" action="urlofserver">
<input type="checkbox" name="mycheckbox" value="1">Is it worth?</input>
</form>
The server would receive mycheckbox with the value of 1.
in PHP, this POST variable is stored in an array as $_POST['mycheckbox'] which contains 1.
I just wanted to make a comment on Adriano Silva's comment.
In order to get what he describes to work you have to add "[]" at the end of the name attribute, so if we take his example the correct syntax should be:
<input type = "checkbox" name="BrandID[]" value="1">Ford</input>
<input type = "checkbox" name="BrandID[]" value="2">GM</input>
<input type="checkbox" name="BrandId[]" value="3">Volkswagen</input>
Then you use something like: $test = $_POST['BrandID']; (Mind no need for [] after BrandID in the php code).
Which will give you an array of values, the values in the array are the checkboxes that are ticked's values.
Hope this helps! :)
One reason is to use the ease of working with values in the system.
<input type="checkbox" name="BrandId" value="1">Ford</input>
<input type="checkbox" name="BrandId" value="2">GM</input>
<input type="checkbox" name="BrandId" value="3">Volkswagen</input>
When the form is submitted, the data in the value attribute is used as the value of the form input if the checkbox is checked. The default value is "on".
$('form').on('change', update).trigger('change')
function update() {
var form = $(this)
form.find('output').text('→ ' + form.serialize())
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form>
<input type="checkbox" name="foo">
<output></output>
</form>
<form>
<input type="checkbox" name="foo" checked>
<output></output>
</form>
<form>
<input type="checkbox" name="foo" value="1" checked>
<output></output>
</form>
<form>
<input type="checkbox" name="foo" value="bananas" checked>
<output></output>
</form>
For the sake of a quick glance answer, from MDN
when a form is submitted, only checkboxes which are currently checked are submitted to the server, and the reported value is the value of the value attribute
It can be confusing because seeing something like
<input type='checkbox' name='activated' value='1'> might lead one to believe that the 1 means true and it will be treated as though it is checked, which is false. The checked attribute itself also only determines if the checkbox should be checked by default on page load, not whether it is currently checked and thus going to be submitted.
We all know how to form a checkbox input in HTML:
<input name="checkbox_name" id="checkbox_id" type="checkbox">
What I don't know -- what's the technically correct value for a checked checkbox? I've seen these all work:
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked>
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="on">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="yes">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="checked">
<input name="checkbox_name" id="checkbox_id" type="checkbox" checked="true">
Is the answer that it doesn't matter? I see no evidence for the answer marked as correct here from the spec itself:
Checkboxes (and radio buttons) are on/off switches that may be toggled
by the user. A switch is "on" when the control element's checked
attribute is set. When a form is submitted, only "on" checkbox
controls can become successful. Several checkboxes in a form may share
the same control name. Thus, for example, checkboxes allow users to
select several values for the same property. The INPUT element is used
to create a checkbox control.
What would a spec writer say is the correct answer? Please provide evidence-based answers.
Strictly speaking, you should put something that makes sense - according to the spec here, the most correct version is:
<input name=name id=id type=checkbox checked=checked>
For HTML, you can also use the empty attribute syntax, checked="", or even simply checked (for stricter XHTML, this is not supported).
Effectively, however, most browsers will support just about any value between the quotes. All of the following will be checked:
<input name=name id=id type=checkbox checked>
<input name=name id=id type=checkbox checked="">
<input name=name id=id type=checkbox checked="yes">
<input name=name id=id type=checkbox checked="blue">
<input name=name id=id type=checkbox checked="false">
And only the following will be unchecked:
<input name=name id=id type=checkbox>
See also this similar question on disabled="disabled".
HTML5 spec:
http://www.w3.org/TR/html5/forms.html#attr-input-checked :
The disabled content attribute is a boolean attribute.
http://www.w3.org/TR/html5/infrastructure.html#boolean-attributes :
The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
Conclusion:
The following are valid, equivalent and true:
<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="ChEcKeD" />
The following are invalid:
<input type="checkbox" checked="0" />
<input type="checkbox" checked="1" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="true" />
The absence of the attribute is the only valid syntax for false:
<input />
Recommendation
If you care about writing valid XHTML, use checked="checked", since <input checked> is invalid XHTML (but valid HTML) and other alternatives are less readable. Else, just use <input checked> as it is shorter.
<input ... checked />
<input ... checked="checked" />
Those are equally valid. And in JavaScript:
input.checked = true;
input.setAttribute("checked");
input.setAttribute("checked","checked");
you want this i think:
checked='checked'
checked
checked=""
checked="checked"
are equivalent;
according to spec checkbox
'----ⓘ checked = "checked" or "" (empty string) or empty
Specifies that the element represents a selected control.---'
It's pretty crazy town that the only way to make checked false is to omit any values. With Angular 1.x, you can do this:
<input type="radio" ng-checked="false">
which is a lot more sane, if you need to make it unchecked.
I think this may help:
First read all the specs from Microsoft and W3.org.
You'd see that the setting the actual element of a checkbox needs to be done on the ELEMENT PROPERTY, not the UI or attribute.
$('mycheckbox')[0].checked
Secondly, you need to be aware that the checked attribute RETURNS a string "true", "false"Why is this important? Because you need to use the correct Type. A string, not a boolean. This also important when parsing your checkbox.
$('mycheckbox')[0].checked = "true"
if($('mycheckbox')[0].checked === "true"){
//do something
}
You also need to realize that the "checked" ATTRIBUTE is for setting the value of the checkbox initially. This doesn't do much once the element is rendered to the DOM. Picture this working when the webpage loads and is initially parsed.
I'll go with IE's preference on this one: <input type="checkbox" checked="checked"/>
Lastly, the main aspect of confusion for a checkbox is that the checkbox UI element is not the same as the element's property value. They do not correlate directly.
If you work in .net, you'll discover that the user "checking" a checkbox never reflects the actual bool value passed to the controller.
To set the UI, I use both $('mycheckbox').val(true); and $('mycheckbox').attr('checked', 'checked');
In short, for a checked checkbox you need:
Initial DOM: <input type="checkbox" checked="checked">
Element Property: $('mycheckbox')[0].checked = "true";
UI: $('mycheckbox').val(true); and $('mycheckbox').attr('checked', 'checked');
Just like all input's, this one also has a 'value' attribute. If you set the value attribute along with the name attribute, it will send ${name}=${value} in the headers. Let's say we had a form with a bunch of stuff and we wanted the user to decide what roles they have, we could use a checkbox. The easiest way is to set the 'value' attribute which will be passed along to the server. Like this:
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" name="my_checkbox" value="is_person">
</form>
The server will receive the following:
my_checkbox=is_person
but only if the checkbox is checked. This would be
my_checkbox=
if it is empty.
This is the exact same with radio inputs.
But.. I have a feeling this isn't what you're asking for... So just encase I'll write another answer below:
If the checked attribute is set to anything (even false) it will be activated, no matter what. The checked attribute doesn't have a specified value, if it's set to anything it will default to 'true' (even if you set it to false).
For example:
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" checked="false"> <!--Still checked-->
</form>
Will be checked even though it's set to false.
<form action="/server" method="post">
<label>Are you a person?</label>
<input type="checkbox" checked="asjdiasjiasdjoasi"> <!--Still checked-->
</form>
Doing this will also check it. It doesn't matter -- as long as it's set it will be checked.
Hope this answers your question, the checked attribute will check the input no matter the value of the attribute.
You can test it here: https://battledash-2.github.io/Live-IDE/
or anywhere like repl.it, or locally.
The technically correct value for a checked checkbox is zero (0), and when the checkbox is not checked, it's index is not defined.
Well, to use it i dont think matters (similar to disabled and readonly), personally i use checked="checked" but if you are trying to manipulate them with JavaScript, you use true/false
I have never seen this, have no idea what is going on:
<form action="/cgi-bin/Lib.exe" method=POST name="slider" ID="Form2">
<input type="text" name="user" value="" ID="Text1">
<input type="text" name="end" value="" ID="Text2">
</form>
function setval()
{
alert(s.getValue());
alert(s2.getValue());
document.slider.user.value = s.getValue();//set value of hidden text box to value of slider
document.slider.end.value = s2.getValue();//set value of hidden text box to value of slider
document.slider.submit();
}
When submitting form from setval(), when I change the name of the first input box from "user" to anything else, my cgi application won't except it and I get an error? I can change the name of the secons input box to anyting and it doesn't seem to have any problem? Confused. Thanks!
Seems more like it's a problem with the cgi than it is with the HTML/Javascript, to me. It probably makes the assumption that a value for "user" will always be sent. Not much else I can tell you without seeing the form-processing code.
Your CGI must be expecting an element called 'user'. You would need to check the source.
I'm really new to HTML, but I can't find anywhere how to return the variable from a check box. I've figured out how to get variables from forms and inputs, but I don't know how to get them from check boxes. Basically, I want a check box that if checked, will return the value yes. If not checked, it doesn't have to return a value, but no would be nice.
When submitting a form, if a checkbox is checked, it will be included in the values collection submitted to the server. If not checked, it will be omitted (as if that checkbox did not exist).
In JavaScript, you can find out whether the checkbox is checked by the checked property:
//returns true or false
var isChecked = document.getElementById('id_of_checkbox').checked;
In ASP.NET, the CheckBox control has a boolean property Checked.
Assign something to the value attribute. You should get the value of the checked box, if there is one in the form values on postback. Note that I've made it a radio input in the case where you want yes or no. For a radio you need to assign the same name, but different ids (if you assign an id at all). You'd want to use checkboxes in the case where you can have more than one value selected or only care to get the value when selected. These types of checkboxes should have different names.
<input type="radio" id="radio_yes" name="radio_btn" value="Yes" /> Yes
<input type="radio" id="radio_no" name="radio_btn" value="No"
checked="checked" /> No
If you only want a single check box with the value yes to be returned if checked, then you can use a check box. You won't get any value if it isn't checked.
<input type="checkbox" id="chk_box" name="chk_box"
value="Yes" /> Do you want this?
On the server-side, you look for the value corresponding to the "radio_btn" (first example) or "chk_box" (second example) key in your form parameters.
Use the 'checked' property.
var checkbox = document.getElementById('checkboxId');
var checked = checkbox.checked;
look at the value of YourCheckboxName.Checked
If a checkbox is disabled, it will be omitted in the values collection submitted to the server even if it is checked:
<input type="checkbox" name="checkbox1">
<input type="checkbox" name="checkbox2" checked>
<input type="checkbox" name="checkbox3" disabled>
<input type="checkbox" name="checkbox4" disabled checked>
Looks like:
result of HTML sample code
Only checkbox2 is in the values collection submitted to the server, if the user submits the form without any changes.