Passing array of data to other page using session in PHP - php

Question

I have some problem passing array of data in Php using session:
In my class, I have this function:
public function check_dupID($id)
{
$this->stmt="select id from student where id='$id'";
$this->res = mysql_query($this->stmt);
$this->num_rows = mysql_num_rows($this->res);
if($this->num_rows == 1)
{
while($this->row = mysql_fetch_array($this->res))
{
$dup_id = $this->row[0];
return $dup_id;
}
}
}
This code checks for duplicate ID of a student. Now, the reason for this is that I uploaded the file in the database using ".csv" file.
Before Uploading it I put all the data in the csv file into an array. Now, I check it one by one:
//created the variable for checking
$id = $check->check_dupID($array[0]);
if($id == TRUE)
{
session_start();
$_SESSION['id']; = $id;//passing it to the next back to array again.
$redirect->page($error);
}
Now when it redirect it gives me the result of an "Array" and if I parse it using foreach it shows only one id but there is more than of that. I want to know how to display it all.

Answer 1

This code will return the duplicate id when it is found for the first time. If you want to return all the duplicate ids, then add them into an array using the while loop and then return it.
To do this modify your code like this:
public function check_dupID($id)
{
$this->stmt="select id from student where id='$id'";
$this->res = mysql_query($this->stmt);
$this->num_rows = mysql_num_rows($this->res);
$dup_id = array();// added here to prevent invalid argument supplied to foreach loop error if nothing is found
if($this->num_rows >1)
{
while($this->row = mysql_fetch_array($this->res))
{
$dup_id[] = $this->row[0];// adding duplicates into the array
}
return $dup_id;
}
}

Answer 2

This code fixes my problem:
if($id == TRUE)
{
$get_id = array();
$get_id[] = $id;
session_start();
$_SESSION['id']; = $get_id;//passing it to the next back to array again.
$redirect->page($error);
}