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Submit form with Javascript then handle with PHP

Not sure how I did this last time or else I wouldnt asking here but here is what I'm trying to do.
I have the usual basic form with a javascript function that will submit the form. Question is that after the form is submitted, I have an if statement in PHP that echos a that the form has been submitted. Any help would be greatly appreciated.
//PHP
if($_POST['submitDelete']){
echo "welcome, You form has been submitted";
}
//HTML
<form id="form_id" action="" method="POST">
First name: <input type="text" name="fname"><br>
Last name: <input type="text" name="lname"><br><br>
<input type="hidden" name="submitDelete" TYPE="submit">
</form>
<button type="button" onclick="myFunction()">Submit</button>
//JAVASCRIPT
<script>
function myFunction() {
document.getElementById("form_id").submit();
}
</script>
I can't seem to trigger the if statement in PHP. I also tried using the form name in the if statement and that didnt work either.

A form element must be told where to submit its data to when the submit event takes place. This is accomplished by setting the action attribute value for the form. Leaving that attribute empty does not implicitly set the form to post back to the current page. So, if you want to have a single page form/form processor, you need the action to be set to the current page file name:
<form action="currentPageFileName.php" method="post">
Next, there's no reason a single page can't have multiple forms on it. In that case you would need multiple submit buttons, each tied to a specific form. For this reason, you can't just drop a submit button anywhere on the page that you like unless you add the form attribute to the button to tie it back to the form it is supposed to trigger the submit for. Also, if you simply place the submit button within the form element it "belongs" to, you don't have to worry about this.
Also, you have some invalid HTML with:
<input type="hidden" name="submitDelete" TYPE="submit">
An element may not have the same attribute repeated within it (the case that you type the attribute in makes no difference since HTML is not case-sensitive). So, that code would wind up simply creating a submit button.
Lastly, if all you want to do with your submit button is cause its related form to be submitted, there is no need for JavaScript at all. That is what submit buttons do by default.
So, in the end, you can get rid of the JavaScript in your code completely and change your HTML to this:
<form id="form_id" action="currentFileName.php" method="POST">
First name: <input type="text" name="fname"><br>
Last name: <input type="text" name="lname"><br><br>
<input type="hidden" name="submitDelete" value="true">
</form>
<button type="submit" form="form_id">Submit</button>

How to send value from JS to PHP handler together with values from other form

I have a form with some input buttons(type="text") and submit button. I also want to implement rate function, so I have found plenty of jQuery plugins (for example this one http://www.jqueryrain.com/?ws9XtnKy). But I can't understand, how can I send rate value to .php handler together with other data, which is in a different form, when submit button is clicked. Can somebody explain it to me? Do you have any ready solutions?
<form method="POST" action="test.php">
<input type="text" name="booktitle" placeholder="Title"/>
<input type="submit"/>
</form>'
<script>
var x;
</script>

i want to check form validation by input type button, not by submit, could any one help in this?

i want to only validate the form and don't want to submit it, so that i can use the form values in modifying other part of the same html page by calling a function "myfunction()" after form validation. for this i want to use a button suggest me required code.my code is following :-
<form name="form1">
<input type="text" name="name1" required></input>
<button onclick="myfunction()" ></button> // i want to validation of form by this button
</form>

You can try this by setting onsubmit event of form to return false; as follows:
<form name="form1" onsubmit="return false;">
<input type="text" name="name1" required></input>
<button onclick="myfunction();" ></button>
</form>
This will not submit the form on clicking the button but will execute myfunction() instead.
If you know jQuery, then you can do this as follows:
$('form[name="form1"]').submit(function (event) {
// This will prevent form being submitted.
event.preventDefault();
// Call your function.
myfunction();
});

For maintainability consider adding an event listener to the button by selection instead of inline. When the button is clicked an event object is passed to the callback. Event objects have a number of properties and methods. In this case you're looking for the method "preventDefault" which prevents the default action of the event which in this case is a form submit. An example:
<form name="form1">
<input type="text" name="name1" required />
<button id="my-button"></button>
</form>
document.getElementById('my-button').addEventListener('click', function(e){
e.preventDefault();
var form = document.forms['form1']; //or this.parentNode
//do stuff
}, false);

i have achived this goal by modifying code as follow:-
<form name="form1" onsubmit="myfunction();return false;">
<input type="text" name="name1" required></input>
<button >check form and call function</button>
</form>
by this i am able to check form and call my function and form is also not submitted in this case.
now i want to reset the form without clicking any button. suggest javascript code for this.

HTML form validation by input type button, not by submit.
Try this
<form name="form1" onsubmit="myfunction(); return false;">
<input type="text" name="name1" required></input>
<button type="submit">Submit</button>
</form>

Submit form to another page (which is different from the page used in ACTION)

I have a form like this:
index.php
<form method="post" action="send.php">
<textarea name="msg" id="msg"></textarea>
<input type="submit" value="Send" />
</form>
So, if I enter something in textarea and clicked on "Send", it is submitted to "send.php" page. But I want to include another button for previewing it. That is, when this button is clicked, the above form is submitted to "preview.php" which will be opened in a new blank window/tab (original page ie. index.php will be there intact). This is to display a preview of the message, that the user is going to send.
I do not know how to do this.

Use Javascript to temporarily change the action and target:
<form method="post" action="send.php" id="idOfForm">
<textarea name="msg" id="msg"></textarea>
<input type="submit" value="Send" />
</form>
<button onclick="doPreview();">Preview</button>
<script type="text/javascript">
function doPreview()
{
form=document.getElementById('idOfForm');
form.target='_blank';
form.action='preview.php';
form.submit();
form.action='send.php';
form.target='';
}
</script>

There is now an attribute for the submit input that handles this:
<input type="submit" formaction=”differentThanNormalAction.php”>

Give your form an ID (form1). The action of the current form can be controlled like this:
function setPreview() {
$('#form1').attr('target','_blank')
$('#form1').attr('action','http://yourpreviewurl.php')
$('#form1').submit()
}
function setSubmit() {
$('#form1').attr('target','')
$('#form1').attr('action','http://yourposturl.php')
$('#form1').submit()
}
Have two buttons, both type="button", one to call setPreview and another to call setSubmit

You can use JavaScript to change the action of the form when the button is clicked and then submit it.
Or simply submit the form via AJAX and then redirect after you get a response.

<form onreturn="someJavascriptFunction()" action="" method="">
creating a js function able to open this preview page

How to autosubmit a form in javascript?

I have a form with an input text field which imports data every couple of seconds and display it in the form field , let us say :
<input name="code" id="code" type="text" size="64" maxlength="128" />
and a submit button and my form has the formname form1.
I want the submit button to be clicked as soon as the data in the form field is changed.
I did try to do the following. In the header I did add the follwoing javascript:
<SCRIPT LANGUAGE="javascript">
function send_data()
{
document.form1.submit();
}
</SCRIPT>
and on the form :
<input name="code" id="code" type="text" size="64" maxlength="128" onchange="send_data();" />
but it didn`t work..
Any help ?
Thanks

Something like this would work:
<form action="#">
<input type="" id="input" />
<button type="submit"></button:>
</form>
<script>
function send_data() {
document.forms[0].submit();
}
window.onload = function(){
var input = document.getElementById('input');
input.onchange = send_data;
}
</script>
But I'd add a few caveats:
I'm assuming there is only one form on the page. You would be safer assigning and ID to your form and using getElementById and referencing that instead of document.forms[x]
The change event will only happen after you lose focus on the input, which I probably what you want? Just making sure it's expected behavior
Without knowing why you need to do this, I'd note that it could potentially be very annoying to the user, as submission will trigger a new page load. You may be better off doing a submission via ajax so as not to disrupt the user's browsing. If you do this, I strongly recommend a JS library to handle this.