nested if loop partially working - php

Question

What I am trying to do is simply display the row values. Now suppose if the field 'head_office' dont have the value 'H.O' then I want to display the values of the last row. I tried but cant find any solution. Here is my code: (I have only blocked the php part)
<?php
$mysql_host = 'localhost';
$mysql_user = 'root';
$mysql_password = '123';
$mysql_database = 'sdbms';
$setup_page = './myinstitute.php';
$db = mysql_connect($mysql_host, $mysql_user, $mysql_password);
mysql_select_db($mysql_database, $db);
if(isset($_REQUEST['id'])){
$id=$_REQUEST['id'];
$sql = "SELECT * FROM institute WHERE id =$id";
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
else if(!isset($_REQUEST['id'])){
$sql = 'SELECT * FROM institute WHERE head_office ="H.O"';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
else{
$sql="SELECT * FROM institute";
$result = mysql_query($sql, $db);
$n = mysql_num_rows($result); //counting number of rows
if($n==0){
header('Location: '.$setup_page);
}
else{
$sql = 'SELECT * FROM institute ORDER BY id DESC LIMIT 1';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
}
?>

Answer 1

<?php
$mysql_host = 'localhost';
$mysql_user = 'root';
$mysql_password = '123';
$mysql_database = 'sdbms';
$setup_page = './myinstitute.php';
$db = mysql_connect($mysql_host, $mysql_user, $mysql_password);
mysql_select_db($mysql_database, $db);
$row = array();
if(isset($_REQUEST['id'])) {
$id = (int) $_REQUEST['id'];
if(!empty($id)) {
$sql = "SELECT * FROM institute WHERE id =$id";
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
} else {
$sql = 'SELECT * FROM institute WHERE head_office = "H.O"';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
if(!isset($_REQUEST['id']) && empty($row))
$sql = "SELECT * FROM institute";
$result = mysql_query($sql, $db);
$n = mysql_num_rows($result); //counting number of rows
if($n == 0) {
header('Location: ' . $setup_page);
} else {
$sql = 'SELECT * FROM institute ORDER BY id DESC LIMIT 1';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
}
?>

Answer 2

As $_REQUEST['id'] can only have 2 status, isset and !isset, the else statement will never be used.

Answer 3

I don't understand very well how do you want to do, but it's illogic: the three step don't execute ever. Try it:
if(isset($_REQUEST['id'])){
$id=$_REQUEST['id'];
$sql = "SELECT * FROM institute WHERE id =$id";
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
else if(!isset($_REQUEST['id'])){
$sql = 'SELECT * FROM institute WHERE head_office ="H.O"';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
if(count($row)<=0) {
$sql="SELECT * FROM institute";
$result = mysql_query($sql, $db);
$n = mysql_num_rows($result); //counting number of rows
if($n==0){
header('Location: '.$setup_page);
}
else{
$sql = 'SELECT * FROM institute ORDER BY id DESC LIMIT 1';
$result = mysql_query($sql, $db);
$row = mysql_fetch_array($result);
}
}
Enjoy your code.