Can't get input value with PHP [duplicate]

Now, when I click in button "save", you should type the value in input "6546"

now when i click button save this error appears

Notice: Undefined index: tot in C:\xampp\htdocs\project\add.php on line 120

this code in line 120

if (isset($_POST['savee'])){
$tot = $_POST['tot'];
echo $tot;
}

and this code in HTMl

<input type="button" style="font-weight: bolder;" value="6546" name="tot" class="btn btn-block btn-primary tot" disabled>

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