if statement not working for MYSQL validation check - php

Question

I am using the following code to determine if a user is signed in or not, I have set the field 'first_sign_in' to 0 in the mysql table but I am still receiving the echo 'already signed in for the start of the day when actually it should return 'not signed in for the start of the day'
Could someone help me on where I am going wrong here.
$time = date('h:i:s', time());
$checkifstaffexists = mysql_query("SELECT user_id from staff WHERE pin = 3012");
if (!$checkifstaffexists) {
die('Failed.');
}
if (mysql_num_rows($checkifstaffexists) > 0) {
$checkfirstsignin = mysql_query("SELECT first_sign_in from staff WHERE pin = 3012");
if ($checkfirstsignin == 0) {
echo 'not signed in for start of day</br>';
$checksignintime = mysql_query("SELECT " . date("d") . " " . "_start from staff WHERE pin = 3012");
if($checksignintime > $time) {
echo 'user is late';
$addtolatetable = mysql_query("INSERT INTO lates (user_id, date_time) SELECT user_id, '2014-05-15 12:00:00' from staff WHERE pin = 3012");
//$signuserin = mysql_query(" ");
$changestatustoin = mysql_query("UPDATE staff SET status=1 WHERE pin = 3012");
//redirect
} else {
echo 'user is not late';
//$signuserin = mysql_query(" ")
$changestatustoin = mysql_query("UPDATE staff SET status=1 WHERE pin = 3012");
//redirect
}
} else {
echo 'already signed in for start of day</br>';
$checkifuserisinourout = mysql_query("SELECT status from staff WHERE pin = 3012");
if ($checkifuserisinourout == 0) {
echo 'user is not signed in so we will sign you in';
//$signuserin = mysql_query(" ");
$changestatustoin = mysql_query("UPDATE staff SET status=1 WHERE pin = 3012");
//redirect
} else {
echo 'user is signed in so we will sign you out';
//$signuserout = mysql_query(" ");
$changestatustoout = mysql_query("UPDATE `staff` SET status=0 WHERE pin = '3012'");
//redirect
}
}
} else {
//The user cannot be found
echo 'User doesn\'t exist.';
}

Answer 1

with the line
$checkfirstsignin = mysql_query("SELECT first_sign_in from staff WHERE pin = 3012");
you get back a resource that you have to use to fetch data, for example:
$row = mysql_fetch_assoc($checkfirstsignin);
and with this array ($row) you can work further.
Please check the manpage for mysql_query for further reading...
and since this will be posted all the time: mysql_* methods are deprecated, please use mysqli or pdo.

Answer 2

if ($checkfirstsignin == 0)
Will always equal true if the query succeeds even if there are no matching results.
You need to use mysql_fetch_row or mysql_fetch_array to do that.
while($row = mysql_fetch_assoc($checkfirstsignin)){
if($row['first_sign_in']==0){
//do something
}
}

Answer 3

Write this var_dump( $checkfirstsignin );
after this line $checkfirstsignin = mysql_query("SELECT first_sign_in from staff WHERE pin = 3012");
And you will see the returned result is an array, so it is always false on the next if check.