json_decode（“ true”）应该返回什么？

Question

when I try the following in PHP:

var_dump(json_decode("123"));

var_dump(json_decode("true"));

what I expect is:

NULL

NULL

but what I actually get is:

int(123)

bool(true)

Should "123" and "true" be considered valid JSON strings? Or is it a bug in the implementation of json_decode()?

Thanks.

Answer 1

它们不是有效的JSON文本，但是据记录json_decode函数能够处理JSON片段。

Answer 2

Remember that JSON is basically just javascript, and is literally just a plain-text string. Both PHP and Javascript have true and false constants:

php > var_dump(json_decode(true)); // php constant "true", maps to int 1
int(1)
php > var_dump(json_decode('true')); // php string / javascript constant true
bool(true)
php > var_dump(json_decode('"true"')); // json-encoded string "true"
string(4) "true"

Your "123" may be a PHP string, which leads to some oddities:

php > var_dump(json_encode(123));
string(3) "123"
php > var_dump(json_encode("123"));
string(5) ""123""   // not quite what you'd expect.
php > var_dump(json_encode('123'));
string(5) ""123""   // also somewhat unexpected


php > var_dump(json_decode(123));
int(123)
php > var_dump(json_decode('123'));
int(123)
php > var_dump(json_decode('"123"'));
string(3) "123"

Answer 3

Both results are right.

string(4) "true"

as a JavaScript string should be converted back to bool(true). Same goes for string(3) "123".