Description:
------------
It seems that on php 7.1 (and only on 7.1), with ZTS when you assign a literal value to a variable, you do not get a copy, but a reference. Thus, when we bind to that variable and change it, the *referenced literal itself* is changed! You can see this with the output:

Expected output:

date before 2002-10-20
date after 1982-01-24
date before 2002-10-20
date after 1982-01-24
date before 2002-10-20
date after 1982-01-24

Actual output:

date before 2002-10-20
date after 1982-01-24
date before 1982-01-24
date after 1982-01-24
date before 1982-01-24
date after 1982-01-24

After the first execution of the loop, the underlying literal value "2002-10-20" on line 28 has been changed to "1982-01-24".

Test script:
---------------
<?php
    require_once('connection.inc');
    $conn = db2_connect($database, $user, $password);

    @db2_exec( $conn , "DROP PROCEDURE test147proc" );
    db2_exec( $conn , "CREATE PROCEDURE test147proc ( OUT p5 DATE)
                           LANGUAGE SQL
                           BEGIN
                             SET p5 = '24.01.1982';
                           END" );

    db2_commit( $conn );

    $prep = db2_prepare($conn, "CALL test147proc (?)");
    for( $i=1 ; $i<=3; $i++ ){
        $p5 = "2002-10-20";
        assert($p5 == "2002-10-20");

        db2_bind_param($prep, 1, 'p5', DB2_PARAM_OUT, DB2_CHAR);

        $result = db2_execute($prep);
    }
    db2_close( $conn );
?>


Expected result:
----------------
Test should run without assertion warnings.

Actual result:
--------------
Assertion warnings are printed:

Warning: assert(): assert($p5 == '2002-10-20')