how does method POST processes/excecutes in PHP - php

Question

I am building a web application, I am having lots of confusion when ever I use POST method.
Lets say I have the below code
<?php
$abc = 'abc';
if(some condition){
$abc = 'xyz';
}
if(isset($_POST['submit'])){
header("Location:http://someexample.php/$abc");
die();
}
?>
<form method="POST">
<input type="text" name="textinput" />
<input type="submit" name="submit" value="submit" />
<input type="submit" name="clear" value="clear" />
</form>
so as per my understanding, If I am not wrong.
When I click the SUBMIT / CLEAR button. The PHP file reloads the self page first before redirecting it to the header location.
If I am right. Is there any other way to avoid multiple redirects when we are working on big PHP files. When I have multiple SUBMIT button.
thank you in advance

Answer 1

You are basically redirecting your request to another page. Instead of redirecting the page using header you should use the action attribute of the form.
<form method="POST" action="yourexample.php" id="myForm">
<input type="text" name="textinput" />
<input type="submit" name="submit" value="submit" />
<input type="submit" name="clear" value="clear" />
</form>
the form will redirect you to the second page. If you do not want to reload your page at all you should use ajax. You can use jquery and post your values to another page buy creating a function. In this case your form tag should not have the action attribute or you
should use preventDefault method.
$("#myForm").submit(function(event) {
event.preventDefault();
$.ajax({
type: "POST",
url: url,
data: data,
success: success,
dataType: dataType
});
});
url will be the name of the page to which you want to redirect the user.
The data will be your form. You can use the .serialize() method to get your form data.
var data = $("myForm").serialize();
In success you can define a function on what to do in case of successful result.

Answer 2

Nothing wrong with multiple redirects: this is how traditional web works.
You may get reduce the number of redirects by using AJAX calls though.
Some notes on your pseudo-code:
it is quite useless to echo anything before Location header: noone is supposed to read the message. Not to mention that no output is allowed before headers.
http:// in front of address allowed only in case of fully qualified URI.
so, the code actually have to be
<?php
if(isset($_POST['submit'])){
header("Location: someexample.php");
die();
}
?>

Answer 3

Forms always post to the "action" attribute in it. If you don't want it to post to self, put your form opening tag as <form action="someexample.php" method="post">. The result will be the POST data being sent to someexample.php instead of to the same page as the form.
If you're looking into multiple form options on one page without redirect, take a look into AJAX submits.
The idea would be to send over the form to your receiving file, process the POST data, and return whatever you wanted returned from that process. For example:
$("form").submit( function(event) {
event.preventDefault(); //prevent the file submitting
var formData = $(this).serialize(); //process the form into an array for submission
$.ajax({
url: "receiver.php", //the url of the receiving file
type: "post", //setting method to post
data: formData, //set the data being sent to the form contents
success: function(response) {
$("div").html(response); //set the receiving div to the html you echo'd in the php document
}
});
});
Your receiver.php file can look exactly the same as a normal PHP document receiving POST data, so <?php if(isset($_POST['submit'])) {} ?> will still work exactly as you're expecting, without the page redirects! This solution does require jQuery though.
Edit:
To deal with the questions update of if(criteria) { $abc = 'xyz'; } there are a couple of suggestions.
To keep the asynchronous approach, go with $_SESSION variables. You could set them using the receiver.php and deal with them in the starting document.
To go back to a standard submission method onto the same document, either break your multiple options into radio inputs, checkboxes, or separate forms.
So:
<input type="radio" name="method" value="submit" />
<input type="radio" name="method" value="clear" />
That way you can choose what method to submit there.
Or you can break them into forms:
<form method="post">
<input type="submit" name="submit" value="submit" />
</form>
<form method="post">
<input type="submit" name="clear" value="clear" />
</form>
Finally, you could change the value of a hidden input on click if you wanted to change between submit and clear, so:
The HTML:
<form method="post">
<input type="hidden" id="method" name="method" value="" />
<input type="submit" id="submit" value="submit" name="submit" />
<input type="submit" id="clear" value="clear" name="clear" />
</form>
The jQuery:
$("#submit").click( function(event) {
event.preventDefault();
$("#method").val("clear"); //set the method to clear
$("form").submit(); //submit the form normally
});
$("#clear").click( function(event) {
event.preventDefault();
$("#method").val("submit");
$("form").submit();
});
The PHP:
<?php
if(isset($_POST['submit'])) {
//do something
} elseif(isset($_POST['clear'])) {
//do something else
}