cannot show the result of php file, help me - php

Question

I don't know why it cannot show the result. I have already put isset() Function on it, but the echo string is not come out.
<form method="POST">
<input type="radio" name="colors" value="red" checked="true">
<label id="r">Red</label>
<input type="radio" name="colors" value="green">
<label id="g">Green</label>
<input type="button" name="add" value="Add">
<input type="button" name="clear" value="Clear">
</form>
<?php
if (isset($_POST['add'])) {
if (isset($_POST['colors'])) {
$colorVal = $_POST['colors'];
echo "$colorVal";
}
}
?>

Answer 1

The type of your Add button must be submit also the Clear button has to be reset.
By the way that $POST['colors'] needs to be $_POST['colors'].
<form method="POST">
<input type="radio" name="colors" value="red" checked="true">
<label id="r">Red</label>
<input type="radio" name="colors" value="green">
<label id="g">Green</label>
<input type="submit" name="add" value="Add">
<input type="reset" name="clear" value="Clear">
</form>
<?php
if (isset($_POST['add'])) {
if (isset($_POST['colors'])) {
$colorVal = $_POST['colors'];
echo "$colorVal";
}
}
?>
Update: (the reset button works as expected)
<form method="POST">
<input type="radio" name="colors" value="red" checked="true">
<label id="r">Red</label>
<input type="radio" name="colors" value="green">
<label id="g">Green</label>
<input type="submit" name="add" value="Add">
<input type="reset" name="clear" value="Clear">
</form>

Answer 2

<form method="POST">
<input type="radio" name="colors" value="red" checked="true">
<label id="r">Red</label>
<input type="radio" name="colors" value="green">
<label id="g">Green</label>
<input type="submit" name="add" value="Add">
<input type="reset" name="clear" value="Clear">
</form>
<?php
if(isset($_POST['add']))
{
if(isset($_POST['colors']))
{
$colorVal = $_POST['colors'];
echo "$colorVal";
}
}
?>
Defines a submit button (for submitting the form) by making its type as SUBMIT
<input type="submit">
The <input type="button"> defines a clickable button (mostly used with
a JavaScript to activate a script).
Also, you have a syntax error for $_POST