json_encode json_force_object问题

<?php
var_dump(json_encode(array("Apple", "Banana", "Pear"))); 
//string(25) "["Apple","Banana","Pear"]"

var_dump(json_encode((object)array("Apple", "Banana", "Pear")));
//string(37) "{"0":"Apple","1":"Banana","2":"Pear"}"

var_dump(json_encode(array("Apple", "Banana", "Pear"),JSON_FORCE_OBJECT));
//string(37) "{"0":"Apple","1":"Banana","2":"Pear"}"

var_dump(json_encode(array(0=>"APPLE",1=>"BABABA")),JSON_FORCE_OBJECT);

//string(18) "["APPLE","BABABA"]"

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最后两行：

var_dump(json_encode((object)array(0=>"APPLE",1=>"BABABA",2=>'PEAR')));
// string(37) "{"0":"APPLE","1":"BABABA","2":"PEAR"}"
var_dump(json_encode(array(0=>"APPLE",1=>"BABABA",2=>'PEAR')),JSON_FORCE_OBJECT);
string(25) "["APPLE","BABABA","PEAR"]"
int(16)

int (16) 是个啥？？加了json_force_object也不好使呢，如果下标不以0开头，或者key不连续，就是object，否则就是数组，哪位前辈给大概解释下为啥，为啥。

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请仔细对比以下两行

var_dump(json_encode(array(0=>"APPLE",1=>"BABABA",2=>'PEAR')),JSON_FORCE_OBJECT);
var_dump(json_encode(array(0=>"APPLE",1=>"BABABA",2=>'PEAR'),JSON_FORCE_OBJECT));