Why PHP isn't use the variable declared outside of POST?

Question

I need some help about how to pass a variable with POST without using sessions.

Currently my code doesn't display value of the variable called $myvariable:

<?php
if(isset($_POST['testbutton'])){
if ($_POST['testbutton'] == 'Testing') {

echo $myvariable;
var_dump($_POST);

}
}

$myvariable = "hello world";

echo '<form action="'.htmlspecialchars($_SERVER["PHP_SELF"]).'" method="post">';
echo '<input type="submit" value="Testing" name="testbutton"/>';
echo '</form>';

?>

What should I change in the code to be able to use $variable in POST['testbutton'] part of the code ?

you're trying to call `$myvariable` before you define it. Move `$myvariable = "hello world";` to the top — WheatBeak, Mar 03 '16 at 20:05
PHP statements are executed in order. Why would you think you can use the result of an assignment before the assignment? — Barmar, Mar 03 '16 at 20:05
If you want to pass a variable using POST, add a hidden input to the form and get its value inside the `if` statement. — jeroen, Mar 03 '16 at 20:06
And no need to use it `if ($_POST['testbutton'] == 'Testing') {` — devpro, Mar 03 '16 at 20:09

WheatBeak · Accepted Answer · 2016-03-03T20:15:59.280

2

Per my comment:

<?php

$myvariable = "hello world";

if(isset($_POST['testbutton'])){
    if ($_POST['testbutton'] == 'Testing') {

        echo $myvariable;
        var_dump($_POST);

    }
}



echo '<form action="'.htmlspecialchars($_SERVER["PHP_SELF"]).'" method="post">';
echo '<input type="submit" value="Testing" name="testbutton"/>';
echo '</form>';

?>

UPDATE

If what you're trying to do is pass a variable from the page to $_POST you'll need to do as jeroen suggested and set a hidden input like this:

  echo '<input type="hidden" value="' . $myvariable .'" name="myvariable"/>';

this will then become $_POST["myvariable"]

edited Mar 03 '16 at 20:15

answered Mar 03 '16 at 20:08

WheatBeak

1,036
6
12

1

I don't think this is what the OP wants, but it's not exactly clear from the question... – jeroen Mar 03 '16 at 20:09
I think no need to use this `if ($_POST['testbutton'] == 'Testing') {` – devpro Mar 03 '16 at 20:10

score 2 · Answer 2 · answered Mar 03 '16 at 20:09

<?php

// define $mvvariable here and PHP will not bring undefined error
$myvariable = "hello world";

if(isset($_POST['testbutton'])){
if ($_POST['testbutton'] == 'Testing') {

echo $myvariable;
var_dump($_POST);

}
}


echo '<form action="'.htmlspecialchars($_SERVER["PHP_SELF"]).'" method="post">';
echo '<input type="submit" value="Testing" name="testbutton"/>';
echo '</form>';

?>

Why PHP isn't use the variable declared outside of POST?

2 Answers2