Echo语句打印值'1'

When I wanted to test whether the value is properly passed from HTML form to PHP, I found something is wrong with the echo statement. Here is the HTML text box code

<div class = form-group>
                    <label for = 'bcaa'>BCAA 5gms Cost</label>
                    <input type = 'text' class = 'form-control' name = 'bcaa'>
                </div>

And here is the PHP code to get the value and print it simply.

<?php

$bcaacost = isset($_POST['bcaa']) ;
echo $bcaacost;
?>

The value given in the text box is not printed, but simply '1' is printed the more echo statement is added more no of '1' is printed

Like

echo "something";
echo "blah blah";

The output is

11

What's the reason for this and what do I need to do to fix this?

isset() returns true or false depending on the variable set or not.

$bcaacost = isset($_POST['bcaa']) ; // return true / 1
echo $bcaacost; // prints 1

it should be like -

if(isset($_POST['bcaa'])) {
    echo $_POST['bcaa'];
}

Or if you want to print some default, then -

$bcaacost = isset($_POST['bcaa']) ? $_POST['bcaa'] : 'Default';
echo $bcaacost;

Remove isset() for variable assigning as it checks veriable $_POST['bcaa'] is set or not.

$bcaacost = $_POST['bcaa'];

Full code

<?php
$bcaacost = $_POST['bcaa'];
echo $bcaacost;
?>

Read more about isset()

if(isset($_POST['bcaa'])) {
    $bcaacost = $_POST['bcaa'] ;    
    echo $bcaacost ;
}

Otherwise, isset($_POST['bcaa']) will print 1 or 0

isset() checks that a variable exists, and returns either true(1) or false(0)

To see the contents of $_POST['bcaa'] you need to check it exists i.e. isset() but then use the contents of the variable

<?php
$bcaacost = isset($_POST['bcaa']);
if ( $bcaacost ) {
    echo $_POST['bcaa'];
}
?>

Or more simply

if ( isset($_POST['bcaa']) ) {
    echo $_POST['bcaa'];
}

As to your suggestion that :

echo "something";
echo "blah blah";

will create 11 that cannot be so. Something else must be causing this or you are just confused as to what is creating the 11 output

the result of isset is true or false. In your case the result is true and it assigned back to $bcaacost and that's why it echoing 1.

use following code:

<?php

$bcaacost = isset($_POST['bcaa'])?$_POST['bcaa']:"not set";
echo $bcaacost;
?>