Header, logic and database - php

Question

I am having an issue with my header location. I am new to php and I am unable to redirect to my index page after this separate php file is run. In addition my function is unable to tell whether the contents of a text box is blank or equal to the default value of "<>".
Thank you
<?php
include('connectionFile.php');
//test for duplicate emails
$query="SELECT * FROM ClientEmail WHERE ClientEmailAddress = '$_POST[emailAdd]'";
$email=$_POST['emailAdd'];
$result=mysql_query($query);
$num=mysql_num_rows($result);
if($num==0)
{
if(isset($_POST['emailAdd']) && !empty($_POST['emailAdd']) && $_POST['emailAdd'].value != "<<please enter email>>")
{
// the form was submitted
//remove hacker HTML
$email2=strip_tags($_POST['emailAdd']);
//Insert data into database
$sql2="INSERT INTO ClientEmail SET ClientEmailAddress='$email2'";
$result=mysql_query($sql2);
//Direct back to homepage
echo "heloooo";
header('location:/index.php');
}
else
{
header('location:/index.php');
}
}
else
{
header('Location:http://www.google.com');
`enter code here`}
?>
EDIT
After making the changes suggested my error log is as follows
Notice: Use of undefined constant db_selected - assumed 'db_selected' in /home/clubbtpk/public_html/connectionFile.php on line 15
Warning: Cannot modify header information - headers already sent by (output started at /home/clubbtpk/public_html/connectionFile.php:15) in /home/clubbtpk/public_html/addEmail.php on line 28
The code in the connection file is:
<?php
$host="localhost";
$username="username";
$password ="password";
// Create connection to mysql server
$con=mysql_connect("$host","$username","$password");
// Check connection
if (!$con)
{
die ("Failed to connect to MySQL: " . mysql_error());
}
// Select database
$db_selected = mysql_select_db("DB", $con);
if(!db_selected)
{
die ("Cannot connect : " . mysql_error());
}
?>
EDIT 2
Resolved first error by changing
if(!db_selected)
to
if(!$db_selected)
RESOLVED
Added the following line of code to my index.php file:
<?php
if(isset($_REQUEST["emailAdd"])){
include("addEmail.php");
}
?>
Then changed the action of the form to "" so that it reloads the current page:
<form name="emailAddr" method="post" action="">

Answer 1

You must not output anything before your redirect.
So this is not allowed:
echo "heloooo";
header('location:/index.php');
EDIT: You should definitely enable error_reporting on your script. I found another error in your query:
$query="SELECT * FROM ClientEmail WHERE ClientEmailAddress = '$_POST[emailAdd]'";
should be
$query="SELECT * FROM ClientEmail WHERE ClientEmailAddress = '" . $_POST['emailAdd'] . "'";
Furthermore you should not use the mysql_* functions anymore but upgrade to mysqli_* functions. And always check the inputted data before inserting them into sql-queries.
EDIT2: Add this at the beginning of your script:
ini_set('display_errors',1);
ini_set('display_startup_errors',1);
error_reporting(-1);
EDIT3:
You have to change this line too:
if(isset($_POST['emailAdd']) && !empty($_POST['emailAdd']) && $_POST['emailAdd'].value != "<<please enter email>>")
Should be:
if(isset($_POST['emailAdd']) && $_POST['emailAdd'] != "<<please enter email>>")
If you would turn error_reporting on you would see it yourself.