Question

When php returns a serialized string, does it only rely on the input value or do outside sources (the environment) play any part at all?

The reason why I am asking this is, I am seeing some arrays that I believe to be identical get serialized slightly different per session.

I wrote this which demonstrates that they are always the same within the same session:

<?php
    $arr = array("something here", "foo" => "something else", "bar" => array( "nested" => "temp", 5232), 3434);

    $s = serialize($arr);

    for( $i = 1; $i <= 100; $i++ )
    {
        $s2 = serialize($arr);
        if( $s2 != $s )
        {
            echo "They are not always the same";
            break;
        }
        if($i == 100)
        {
            echo "They are always the same";
        }
    }
?>

So either there is something causing them to be created differently on different connections, or my arrays that appear to be identical are somehow not.

Answer 1

Serialized strings are human readable. They can be broken down as follows:

a:2:{i:0;s:14:"something here";}

The first letter is the datatype, array, the number is the length/size of the object. So next up you have an integer of 0 and then a string 14 characters in length. So now you can read the format can you see any differences?

When I run your code on codepad it works as expected. So perhaps there is more at play here like in your actual code you are trying to serialize an object.