Unable to INSERT any records in MYSQL from PHP - php

Question

So I am trying to develop an app and I need an API, so I am trying now PHP in order to pass my variables from the app to the MYSQL. I am trying with $_GET first in order to see if everything works fine. I tried to pass variables to the database through MYSQL Workbench and then from the app and worked fine. But, when I emptied the table and tried again it didn't work! So I am guessing that my loop doesn't respond well to the fact that my table is empty(?)
This is the code that checks for the email and username if exists and if not insert the variables:
$result = 'notSet';
$query=mysql_query("SELECT * FROM project");
while ($row = mysql_fetch_assoc($query)) {
if(strcmp($row['email'],$email)==0){ //strcmp uses two strings and it returns an integer, if 0 then no differences if more than 0 then there are
$result = 'Email exists';
}else{
if(strcmp($row['username'],$username)==0){
$result = 'Username exists';
}else{
//encryption
$insert = mysql_query("INSERT INTO project VALUES ('$userid', '$fullname','$username','$password','$course','$year','$age','$email')");
$result = 'Registered';
session_start();
$session = session_id();
$SESSION['username']=$username;
}
}
}
Any ideas??

Answer 1

Your table is empty. $query is returning false. Because of this your loop is not executed. You should change the code like this:
if($query){
while(){
//check username and email
}
}
else{
// execute insert query
}
Can you try this code:
$result = 'notSet';
$query = mysql_query("SELECT * FROM project WHERE email = '$email' OR username = '$username' ");
if(mysql_num_rows($query) === 0 ){
$insert = mysql_query("INSERT INTO project VALUES ('$userid', '$fullname','$username','$password','$course','$year','$age','$email')");
$result = 'Registered';
session_start();
$session = session_id();
$SESSION['username']=$username;
}
else{
$result = 'Username or Email exists';
}

Answer 2

We should add single quotes ' only if field type is not integer type. For eg if userid field is integer type and rest of fields are not integer type then query will be
$insert = mysql_query("INSERT INTO project VALUES ($userid, '$fullname','$username','$password','$course','$year','$age','$email')") or die(mysql_error());
thanks

Answer 3

First: you should switch to PDO or mysqli, because the mysql_* functions are deprecated. Please follow the links in Shais comment.
To get the INSERT done, you've got to change your logic. With your code right now, it will never be executed for an empty resultset. You could do it so:
$query=mysql_query("SELECT * FROM project");
if (mysql_num_rows($query) > 0) {
// we've got results, let's loop through the resultset
while($row = mysql_fetch_assoc($query)) {
// do something with the result
}
}
else {
// we've got no results,
// do the insert
}
mysql_query will return a resource for SELECT type queries. A resource evaluates in PHP to true. You can use mysql_num_rows() to check, whether your resultset is not empty.
Excerpt from the linked manual:
Use mysql_num_rows() to find out how many rows were returned for a
SELECT statement
PS: Please consider the content of the red box.

Answer 4

<?php
$query=mysql_query("INSERT INTO project set id=$userid,
'fullname'=$fullname,
'username'=$username,
'password'=$password,
'course'=$course,
'year'=$year,
'age'=$age,
'email'=$email
");
?>