<input type="text" id="prName" name="prName" style="color:black;" size="25">

var prodNumber = '123ABC456BGR'; // create variable with product number

document.getElementById('prName').value = "<?php

    $servername = "?????????";
    $username = "???????";
    $password = "?????";
    $dbname = "????";
    $phpvar = '"+prodNumber+"';




    // Create connection
    $con = mysqli_connect($servername, $username, $password, $dbname);

    if (!$con) {
        die("Connection failed: " . mysqli_connect_error());
    }

    $sql = "SELECT * FROM unitslist WHERE Part_Number = '".$phpvar."'";

    $result = mysqli_fetch_assoc(mysqli_query($con, $sql));

    $myStr = $result['Product_Name'];

    echo $myStr;


    mysqli_close($con);

    ?>"