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Asked: 2026-06-13T19:04:35+00:00

I have a form which has a select tag; on selection of an item

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I have a form which has a select tag; on selection of an item from the drop down rest of the form fields should get filled accordingly.Note that all the form data comes from mysql database. Below is my code :

    <script language="javascript" type="text/javascript">
            function populateData($id)
            {
                alert('in populateData');
                y = document.getElementById("selectCard");
                document.getElementById("to_address").value = to_address[y.selectedIndex];
                document.getElementById("subject").value = subject[y.selectedIndex];
                document.getElementById("email_content").value = email_content[y.selectedIndex];
            }
    </script>
    <body>
        <?php
            mysql_connect("localhost", "someUser", "password") or die("Connection Failed");
            mysql_select_db("mns")or die("Connection Failed");
            $query = "SELECT * FROM table";
            $result = mysql_query($query);
        ?>              
        <select id="selectCard" class="dropdown" onchange="populateData($id)">
            <?php
                while ($line = mysql_fetch_array($result, MYSQL_ASSOC)) {
            ?>  
            <option value="<?php echo $line['source_name'];?>"> <?php echo $line['source_name'];?>
            <?php
                $id = $line['source_id'];           
                $source_name = $line['source_name'];
                $source_email = $line['source_email'];
                $phone_no = $line['source_id'];
                $disteller_function = $line['disteller_function'];
                }
            ?>
        </select>               
        <P><INPUT ID="to_address" TYPE="TEXT" NAME="to_address" SIZE="25"></P>    
        <P><INPUT ID="subject" TYPE="TEXT" NAME="subject" SIZE="25"></P>         
        <P><INPUT ID="email_content" TYPE="TEXT" NAME="email_content" SIZE="500"></P>         
        <P><INPUT TYPE="SUBMIT" VALUE="Submit" NAME="B1"></P>                       
    </body>

When am passing ‘$id’ as parameter, the ‘populateData($id)’ function is not getting called.And When i remove the parameter the code works but i get ‘undefined’ in rest of the form fields.

Any help is much appreciated.

Nanashi

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1 Answer

  1. Editorial Team

    First of all, it seems weird that you pass the parameter $id to populateData() since you are not using it anywhere inside that function. Maybe you should recheck your code and see if it matches your design, what you really want to do and how it should be done.

    The reason your call is not working is PHP variables must start with $ but Javascript variables can’t and most importantly: You can’t just have a reference to a server side PHP script variable on your client side Javascript code. You need to have your PHP server side script echoing (outputting) the value of your PHP script variable $id as the parameter id on a function call of the HTML+Javascript code which the user’s browser will receive and run client side (can be done without the single quotes if $id is a number and you want to pass it as a numeric value to populateData()).

    Just remove the $ from your parameter $id on the function declaration and set it between PHP tags inside single quotes to echo it as a string parameter to the function calling on the HTML output:

    function populateData(id){
...
}
...
<select id="selectCard" class="dropdown" onchange="populateData('<?php echo $id; ?>')">

    Also I recommend you testing with Javascript console opened in the browser (i.e. Web Developer -> Web Console or CTRL+SHIFT+K in Firefox), which can help you track future bugs like this on the fly.

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