13.8. Changes in Functions

Some minor changes in functions break backward compatibility. There are countless other additions to functions and additional functions, but these do not affect compatibility between PHP 4 and PHP 5.

13.8.1. array_merge()

This function no longer accepts a non-array parameter as one of its arguments. In PHP 4, it was perfectly valid to use scalar types, like an integer or string (but not a variable representing "null"), as parameter. These types are happily included as an element in the resulting array. PHP 5 no longer supports this. If you use a scalar type, PHP 5 issues an error of type E_WARNING and return an empty array. You can see this behavior by comparing the output of this script from PHP 4 and PHP 5:

<?php
    $array1 = array (1, 2, 3, 4);
    $array2 = null;
    $array3 = 'non-array';
    $array4 = array ('a', 'b', 'c');

    print_r(array_merge($array1, $array2, $array3, $array4));
?>

Array
(
    [0] => 1
    [1] => 2
    [2] => 3
    [3] => 4
    [4] => non-array
    [5] => a
    [6] => b
    [7] => c
)

Warning: array_merge(): Argument #2 is not an array in /13-making 
the-move/array_merge.php on line 7

Warning: array_merge(): Argument #3 is not an array in /13-making 
the-move/array_merge.php on line 7

13.8.2. strrpos() and strripos()

strrpos() and strripos() search for the last occurrence of a string inside a string in a respectively case-sensitive and case-insensitive way. In PHP 5, the full $needle is searched for in the string, searching from the end rather than the first character of this $needle string, as in PHP 4. The following example shows this:

<?php
    $str = "This is a short string.";


    var_dump(strrpos($str, "small"));
?>

In PHP 4, this returns position 16 (the index of the "s" of "string"):

int(16)

In PHP 5 this returns

bool(false)

It is possible that more functions broke compatibility between PHP 4 and PHP 5, but they are either not known, a bug fix, or are too unimportant to be noticed.