updating mysql by id - php

Question

I'm new to PHP and after looking on the web for the last hour I couldn't find out what was wrong with my code so I come to you. Im trying to have a place to update my data collected from a from. I get this error. Undefined index: id in /Users/mm1/Desktop/php/backend form/edit_ac.php on line 12. Here is what I have so far. Can someone please help..
<?php require("database.php"); ?>
<?php require("functions.php"); ?>
<?php
ini_set('display_errors', 'On');
error_reporting(E_ALL | E_STRICT);
// Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
$id= mysql_prep($_GET['id']);
$last= mysql_prep($_POST['last']);
$first= mysql_prep($_POST['first']);
// update data in mysql database
$sql="UPDATE $tbl_name SET first='{$first}', last='{$last}' WHERE id='{$id}'";
$result=mysql_query($sql);
// if successfully updated.
if($result){
echo "Successful";
echo "<BR>";
echo "<a href='edit_info.php'>View result</a>";
}
else {
echo "ERROR";
}
?>
Here is the form (I know it all isn't complete I'm just trying to get it to work first.)
<?php require("database.php"); ?>
<?php // Connect to server and select database.
mysql_connect("$host", "$username", "$password")or die("cannot connect");
mysql_select_db("$db_name")or die("cannot select DB");
// get value of id that sent from address bar
$id=$_GET['id'];
// Retrieve data from database
$sql="SELECT * FROM $tbl_name WHERE id='$id'";
$result=mysql_query($sql);
$rows=mysql_fetch_array($result);
?>
<form name="form1" method="post" action="edit_ac.php">
<table width="700" border="0" cellpadding="5">
<tr>
<td colspan="2" class="center"><h3>PARTICIPANT IDENTIFICATION</h3></td>
</tr>
<tr>
<td width="218">First</td>
<td width="456"><input name="first" type="text" maxlength="50" id="first" value="<? echo $rows['first']; ?>" /></td>
</tr>
<tr>
<td width="218">Last</td>
<td width="456"><input name="last" type="text" maxlength="50" id="last" value="<? echo $rows['last']; ?>" /></td>
</tr>
<tr>
<td width="218">Middles</td>
<td width="456"><input name="middle" type="text" maxlength="50" id="middle" value="<? echo $rows['middle']; ?>"/></td>
</tr>
<tr>
<td>Address</td>
<td><input name="address" type="text" maxlength="50" id="address" value="<? echo $rows['address']; ?>"/></td>
</tr>
<tr>
<td>City</td>
<td><input name="city" type="text" maxlength="50" id="city" value="<? echo $rows['city']; ?>"/></td>
</tr>
<tr>
<td>State</td>
<td><input name="state" type="text" maxlength="15" id="state" value="<? echo $rows['state']; ?>"/></td>
</tr>
<tr>
<td>Zip</td>
<td><input name="zip" type="text" maxlength="15" id="zip" value="<? echo $rows['zip']; ?>" /></td>
</tr>
<tr>
<td>Home Phone</td>
<td><input name="home_phone" type="text" id="home_phone" value="<? echo $rows['home_phone']; ?>" /></td>
</tr>
<tr>
<td>Daytime Phone</td>
<td><input name="daytime_phone" type="text" id="daytime_phone" value="<? echo $rows['daytime_phone']; ?>" /></td>
</tr>
<tr>
<td>Email Address</td>
<td><input name="email_address" type="text" id="email_address" value="<? echo $rows['email_address']; ?>" /></td>
</tr>
<tr>
<td>Birthday</td>
<td><input name="month" type="text" id="month" size="3" maxlength="2" value=""/> / <input name="day" type="text" id="day" size="3" maxlength="2" value=""/> / <input name="year" type="text" id="year" size="5" maxlength="4" value=""/></td>
</tr>
<tr>
<td>Social Security Number</td>
<td><input name="ss_1" type="text" id="ss_1" size="5" maxlength="3" value=""/> - <input name="ss_2" type="text" id="ss_2" size="5" maxlength="2" value=""/> - <input name="ss_3" type="text" id="ss_3" size="5" maxlength="4" value="" /></td>
</tr>
<tr>
<td colspan="2" class="center"><h3>PHOTO IDENTIFICATION </h3></td>
</tr>
<tr>
<td>Type of ID</td>
<td>
<input type="text" name="type_of_id" id="type_of_id" value=""/></td>
</tr>
<tr>
<td>ID Number</td>
<td>
<input type="text" name="id_number" id="id_number" value="" /></td>
</tr>
<tr>
<td>Issuing Jurisdiction</td>
<td><input type="text" name="issuing_state" id="issuing_state" value=""/></td>
</tr>
<tr>
<td>Expiration Date</td>
<td><input type="text" name="expiration_date" id="expiration_date" value=""/></td>
</tr>
<tr>
<td>Issue Date</td>
<td><input type="text" name="issue_date" id="issue_date" value="" /></td>
</tr>
<tr>
<td colspan="2" class="center"><h3>ESTABLISHING YOUR ACCOUNT</h3></td>
</tr>
<tr>
<td colspan="2" class="center">Designate Account Type</td>
</tr>
<tr>
<td>
Acount Type
</td>
<td>
<label>
<input type="radio" name="traditional" value="1" id="traditional" />
Traditional</label>
<br />
<label>
<input type="radio" name="roth" value="1" id="roth" />
Roth</label>
<br />
<label>
<input type="radio" name="sep" value="1" id="sep" />
SEP</label>
<br />
<label>
<input type="radio" name="simple" value="1" id="simple" />
SIMPLE</label>
<br /></td>
</tr>
<tr>
<td colspan="2" class="center">Fund Your Account</td>
</tr>
<tr>
<td colspan="2"><input name="rollover" type="radio" value="1" id="rollover" />I will rollover cash from an existing IRA or qualified retirement plan
</td>
</tr>
<tr>
<td>Prior Custodian Plan Name</td>
<td><input name="prior_plan_name" type="text" maxlength="50" id="prior_plan_name" value=""/></td>
</tr>
<tr>
<td>Expected Rollover Amount</td>
<td><input name="rollover_amount" type="text" maxlength="50" id="rollover_amount" value=""/></td>
</tr>
<tr>
<td colspan="2"><input name="transfer" type="radio" value="1" id="transfer" /> I will transfer assets from another IRA and have attached a TRANSFER AUTHORIZATION form </td>
</tr>
<tr>
<td colspan="2"><input name="contribution" type="radio" value="1" id="contribution"/> I have attached a contribution check as follows</td>
</tr>
<tr>
<td>IRA Cash Contribution for the Year</td>
<td><input name="cash_contributions_1" type="text" id="cash_contributions_1" value=""/></td>
</tr>
<tr>
<td>in the amount of</td>
<td><input name="amount_1" type="text" id="amount_1" value=""/></td>
</tr>
<tr>
<td>IRA Cash Contribution for the Year</td>
<td><input name="cash_contributions_2" type="text" id="cash_contributions_2" value="" /></td>
</tr>
<tr>
<td>in the amount of</td>
<td><input name="amount_2" type="text" id="amount_2" value="" /></td>
</tr>
<tr>
<td>Employer OR Employee (circle one) SEP/SIMPLE Contribution for the Year</td>
<td><input name="employer_contributions" type="text" id="employer_contributions" value="" /></td>
</tr>
<tr>
<td>in the amount of</td>
<td><input name="amount_3" type="text" id="amount_3" value="" /></td>
</tr>
<tr>
<td></td>
<td style="text-align:right"><input type="submit" name="Submit" value="Submit"></td>
</tr>
</table>
</form>
</table>
<?php
// close connection
mysql_close();
?>

Answer 1

Add the id into the form as a hidden field.
<input type="hidden" name="id" value="<?php print $rows['id'] ?>">

Answer 2

An undefined index simply means that the index of a certain array doesn't exist. So in this case $_GET has not index of id.
Perhaps you should be checking if the variables are set before anything.
if(!empty($_GET['id']) && !empty($_POST['last']) && !empty($_POST['first'])){
// other code
}
You may also be using the wrong superglobal, like GeoPhoenix said, are you sure it's not $_POST['id'] you're looking for?

Answer 3

If you aren't including the parameters in the call to the page you are getting errors because you turned error reporting all the way up in the first few lines:
ini_set('display_errors', 'On');
error_reporting(E_ALL | E_STRICT);
Often PHP (and therefore PHP tutorials) assume a lower setting where PHP will either throw a warning or ignore index errors on arrays. Therefore when you hit:
$id= mysql_prep($_GET['id']);
$last= mysql_prep($_POST['last']);
$first= mysql_prep($_POST['first']);
It throws an error, but your references might assume it fails quietly.
Your form appears to provide the ID number in the id_number instead of just id. So switching to $id=mysql_prep($_GET['id_number']); is likely to get more effective results.
Since you are new to PHP I also strongly suggest changing your PHP library away from the old mysql lib to either mysqli or PDO. Changes people are suggesting will likley get you the results you expect but not fix the multiple SQL Injection vulnerabilities this script has.

Answer 4

I don't see anything in your form that has the name "id".
If your using $_get['id'] you must have a link or submit button that tranfers to a url that looks like this.
<a href="phpfile.php?id=PUT_VALUE_HERE>
Notice the url has the variable name id after the question mark and you tell what the variable is after the =.
Otherwise if your not going to put your variable in a url. You use $_POST['id'].
In order for $_POST['id'] to work you need an input in your form that has the name attribute set to id. For example
<input name="id" type="text">
I do not see anything in your form with a name attribute set to "id".