I'm unsure what behaviour exactly that you're indicating needs to be documented. 
Could you please provide some example code, so that we do not need to guess at 
what needs to be documented?

Here a example code :

#!/usr/bin/php
<?php
$toto = array("toto", "titi", "tata");
var_dump($toto);

var_dump(json_encode($toto));

unset($toto[1]);

var_dump($toto);

var_dump(json_encode($toto));
?>

The output :


array(3) {
  [0]=>
  string(4) "toto"
  [1]=>
  string(4) "titi"
  [2]=>
  string(4) "tata"
}
string(22) "["toto","titi","tata"]"
array(2) {
  [0]=>
  string(4) "toto"
  [2]=>
  string(4) "tata"
}
string(23) "{"0":"toto","2":"tata"}"

The first json_encode convert $toto to an array. And the second, after delete 
the second element, convert $toto to an 
object.

This behavior must be strange when we don't know the JSON definition about array 
and object, explicited here => http://www.json.org/
 * "An object is an unordered set of name/value pairs"
 * "An array is an ordered collection of values"

That's a very interesting behaviour that I wasn't aware of.

http://svn.php.net/viewvc/php/php-src/trunk/ext/json/json.c?
revision=318178&view=markup#l175

This section of code essentially says that if any of the keys are not in 
numerical order, the keys are all treated as strings.

I'll definitely document this.

This bug has been fixed in the documentation's XML sources. Since the
online and downloadable versions of the documentation need some time
to get updated, we would like to ask you to be a bit patient.

Thank you for the report, and for helping us make our documentation better.