This error appears when you try to access an array value and the key is not within the associative array.

Example:

$test = array ("foo" => "bar", "tricky" => "code");

echo $test['foo']; => foo , all fine

echo $test['lanugages'] => error, because there is no key "languages"

No idea. Is your php code executed correctly? Sure there is no typo anywhere?

You can´t use function return values directly as an array. This is your code (an example):

$str = explode( "-", $frm['CUSTOM1'] )[1];
$id = explode( "-", $frm['CUSTOM1'] )[0];

You must save the return value of explode in a variable before you use it. Change your code to something like:

$arrTmp = explode( "-", $frm['CUSTOM1'] );
$str = $arrTmp[1];
$id = $arrTmp[0];

HTH

This could mean you have a problem to set up a mysql connection. Are you sure your username and password are correct?

Try to upload an .htaccess file in your document root like this:

php_admin_flag register_globals on

Sry, I am not a wordpress expert.

I can only tell you the function post_class is missing for some reason...

Please post your full error message.

In your file "database.php" some code is executed to connect to a database.

The given username/password in this code do not match the mysql server (you gave wrong credentials) and therefore no connection is established.

Ask your mysql-administrator or look for some typos in your username/password

your php code calls a function which does not exists. It´s name is "validip". Open all your php files and look for "function validip(", perhaps you just have misspelled it and it should be "valid_ip". Or you have to include a php file, in which the function is defined.

I think it is not php related. A 404 error means that a requested page does not exist.

What page do you request? Is it a file or some mod_rewrite?