Trouble with PHP if else logic and variables - php

Question

So, I have a couple of variables in PHP, and they are generated from different places. $new_ip comes from the following command:
$new_ip = file_get_contents('http://www.ipaddresscheck.comlu.com/ip.php');
And the $old_ip comes from:
$sql = mysql_query('SELECT * FROM ip ORDER BY id DESC LIMIT 1');
$row = mysql_fetch_array( $sql );
$old_ip = $row['current_ip'];
My problem is, I am getting incorrect results from:
if ($old = $new)
{
$different = '1';
}
else {
$different = '2';
}
echo $different;
I ALWAYS get 2, wether the IPs are the same or not; if I use '==' as the comparison, I ALWAYS get 1.
When I run the following code, I get the following output:
var_dump($old_ip);
var_dump($new_ip);
Output
string(15) "123.123.123.123" string(167) "184.6.216.163 "
Are the variables different types? If So, can I make them the same so I am only comparing the IP and not the type? If the IPs are the same I should get '1' and if they are different, I should get '2', right?

Answer 1

Your problem is lurking here:
string(15) "123.123.123.123" string(167) "184.6.216.163 "
^^^
The address retrieved from your database is coming along with 154 unwanted characters. trim() both strings and then do the comparison.
Oh - and you should really shorten the field that stores the IP address. 15 characters should do.

Answer 2

Code
if ($old = $new) // you are using assignment operator here
{
$different = '1';
}
Should be
if ($old == $new) //Equal to operator
{
$different = '1';
}
Also confirm the variable names are
$old and $new or $old_ip and $new_ip

Answer 3

Assignment ( = ): Assigns the value on the right to the variable on the left
Equality ( == ): Checks if the left and right values are equal
Identical ( === ): Checks if the left and right values are equal AND identical (same variable type)
Example:
$a = 1; // Sets the value of $a as the integer 1
$b = TRUE; // Sets the value of $b to the boolean TRUE
if ($a == $b){
echo 'a is equal to b.';
}
if ($a === $b){ // compare VALUE and data type: if $a(integer) === $b(boolean)
echo 'a is identical and equal to b.';
}
if ($a = $b){
echo '$b value to variable $a';
}
In your code i noticed a problem. A space is there in second IP address. so
string(15) "123.123.123.123" string(167) "184.6.216.163 "
^
Trim both IP address.
If not work, then convert it to other datatype and compare.(Just for debugging purpose. :))

Answer 4

OLD :
if ($old = $new){
$different = '1';
}
New Correct :
if ($old == $new){
$different = '1';
}
you are using (=) assignment operation in the place of comparison operation.

Answer 5

As far as I can see the behaviour is normal because you are using $old and $new both are unset.
$new_ip = file_get_contents('http://www.ipaddresscheck.comlu.com/ip.php');
$sql = mysql_query('SELECT * FROM ip ORDER BY id DESC LIMIT 1');
$row = mysql_fetch_array( $sql );
$old_ip = $row['current_ip'];
The next code will always give 2 because $new is unset. What you are doing here is assigning $old the value of $new and since $new is unset $old = $new will always be false.
if ($old = $new)
{
$different = '1';
} else {
$different = '2';
}
echo $different;
In the next example you are actually comparing $old and $new. Since both are unset the expression $old == $new will always be true.
if ($old == $new)
{
$different = '1';
} else {
$different = '2';
}
echo $different;
What you need to do is using the right vars and trim them.
// get new ip and trim white spaces
$new_ip = trim(file_get_contents('http://www.ipaddresscheck.comlu.com/ip.php'));
// get the old ip
$sql = mysql_query('SELECT * FROM ip ORDER BY id DESC LIMIT 1');
$row = mysql_fetch_array( $sql );
$old_ip = $row['current_ip'];
if ($old_ip == $new_ip)
{
$different = '1';
} else {
$different = '2';
}
echo $different;
I am not trimming white spaces on $old_ip because I guess that you will be using $new_ip to update your database and since $new_ip is already trimmed we can be sure that $old_ip has no white spaces.
You should always have php warnings enabled when coding!
It would have popped you a warning because you used unset vars.
PS : note that this code will only work as expected if file_get_contents() returns a IP with white spaces, the output could be different (error output, not able to detect ip correctly, ... etc)