PHP print_r($_SESSION) not output what I expect

Question

I have 1st PHP page named session1.php with code below:

<?php
session_start();

.....mysql connection...

$sql = "SELECT name1, brand, price  FROM products WHERE name1='cuvette' ORDER BY 'name1' ASC,'desc1' ASC";
$result = mysqli_query($con,$sql);

while($row = mysqli_fetch_array($result)) {
$_SESSION['tag'] = $row;
print_r($_SESSION['tag']);
}

It outputs:

Array ( [0] => Cuvette [name1] => Cuvette [1] => HmbG [brand] => HmbG [2] => 9.00 [price] => 9.00 ) 
Array ( [0] => Cuvette [name1] => Cuvette [1] => HmbG [brand] => HmbG [2] => 8.00 [price] => 8.00 )

Then I setup 2nd PHP page named session2.php with code below:

<?php
session_start();
print_r($_SESSION['tag']);
?>

But session2.php only ouputts:

Array ( [0] => Cuvette [name1] => Cuvette [1] => HmbG [brand] => HmbG [2] => 8.00 [price] => 8.00 )

I am expecting the results should be same with session1.php(2 arrays). Anyone has the explanation for this??

Actually you don't have 2 arrays. You are overwriting the first array with the second. — Dinei
– Dinei, Commented Jun 22, 2017 at 3:01
I also want to know: What is the meaning of this[ ] in $_SESSION['tag'][ ] = $row; ? I don't know the meaning that's why not using it. Where can I learn that? — P. Lau
– P. Lau, Commented Jun 22, 2017 at 4:04

LF-DevJourney · Accepted Answer · 2017-06-22 03:30:32Z

1

You call the print_r() in the while loop in the first php file, which may be executed many times, and the session value has been oberrided.

Change your code to this, it will be ok.

$_SESSION['tag'] = [];
while($row = mysqli_fetch_array($result)) {
$_SESSION['tag'][] = $row;

}
print_r($_SESSION['tag']);

edited Jun 22, 2017 at 3:30

answered Jun 22, 2017 at 3:07

LF-DevJourney

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6 Comments

P. Lau Over a year ago

I tried this. I works at first. But if I refresh the page, the array gets double, the refresh again, it gets triple..why??

LF-DevJourney Over a year ago

You can set it to empty array before the while loop.

P. Lau Over a year ago

Now it works. Just a question, dreamweaver mark red on this line red saying syntax errot: $_SESSION['tag'] = []; but is still work. why?

LF-DevJourney Over a year ago

@P.Lau forums.digitalpoint.com/threads/…

P. Lau Over a year ago

I also want to know: What is the meaning of this[ ] in $_SESSION['tag'][ ] = $row; ? I don't know the meaning that's why not using it. Where can I learn that?

|

Obsidian Age · Accepted Answer · 2017-06-22 03:35:09Z

1

Your first page is assigning to $_SESSION['tag'] from inside a while loop:

while($row = mysqli_fetch_array($result)) {
  $_SESSION['tag'] = $row;
}

Because you are assigning to a variable, rather than pushing to an array, each time you make the assignment you are overwriting any existing content stored within the session variable.

To resolve this, you can assign an array directly to a $_SESSION variable, such as:

$_SESSION['tag'] = [];
while($row = mysqli_fetch_array($result)) {
  $_SESSION['tag'][] = $row;
}

The output appears to be correct in the first page, because your print statement is within the while loop. The variable is written to, printed out, then overwritten, and printed out again.

Hope this helps! :)

edited Jun 22, 2017 at 3:35

answered Jun 22, 2017 at 3:03

Obsidian Age

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4 Comments

P. Lau Over a year ago

I tried this. I works at first. But if I refresh the page, the array gets double, the refresh again, it gets triple..why??

Obsidian Age Over a year ago

You need to clear the array beforehand. By setting it as an empty array before adding the result of the query to it, you won't duplicate the data. I've updated my answer to fix this.

P. Lau Over a year ago

I also want to know: What is the meaning of this[ ] in $_SESSION['tag'][ ] = $row; ? I don't know the meaning that's why not using it. Where can I learn that?

Obsidian Age Over a year ago

The square brackets denote an empty array. It's essentially the same thing as array(), with the only difference being that [] is only supported from PHP 5.4 onwards :)

uhowep · Accepted Answer · 2017-06-22 04:08:14Z

0

$_SESSION['tag'] is not an array but a variable.You see two arrays because you run print_r twice.

You can compare the following two codes：

while($row = mysqli_fetch_array($result)) {
    $_SESSION['tag'] = $row;   //This is the assignment of variable
}
print_r($_SESSION['tag']);

And the other is：

while($row = mysqli_fetch_array($result)) {
    $_SESSION['tag'][] = $row;  //This is appending the variable to the array
}
print_r($_SESSION['tag']);

answered Jun 22, 2017 at 4:08

uhowep

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