php json_decode returning infinite

Question

If I run the following, no error is returned and the value of $result is INF. json_last_error() returns 0.

$result = json_decode('547533e683433', true);

As this is a string and not JSON I would expect $result to be NULL and json_last_error() to return 4 or JSON_ERROR_SYNTAX.

Why is this happening?

I would expect json_last_error() to return an error code, in this case it should be 4 (JSON_ERROR_SYNTAX) and the $result to be NULL. I'll update the question. — greg, Jun 11 '15 at 21:11
@RocketHazmat So huge, that PHP thinks it is infinitive and returns it as `INF` — Rizier123, Jun 11 '15 at 21:11
@greg: According to [the docs](http://php.net/json_decode), `[PHP] will also encode and decode scalar types and NULL`. So it's trying to decode `'547533e683433'` as an int, but it's so big that it gives you infinity. — gen_Eric, Jun 11 '15 at 21:13
Not a full dupe: http://stackoverflow.com/q/19236155/3933332 — Rizier123, Jun 11 '15 at 21:14
@greg: It's a number. The `e` means "times `10^y`". So, `3e2` is `3x10^2`. See the docs for [`is_numeric`](http://php.net/manual/en/function.is-numeric.php): Numeric strings consist of optional sign, any number of digits, optional decimal part and optional exponential part. Thus +0123.45e6 is a valid numeric value. — gen_Eric, Jun 11 '15 at 21:15
@greg: Also when decoding, `'1'` is a number and `'"1"'` is a string. — gen_Eric, Jun 11 '15 at 21:21
Why the down votes? It seems like a legitimate question to me? @RocketHazmat your answers have been great, add as an answer and I'll accept. — greg, Jun 11 '15 at 21:22
@greg I think the problem was, that the users, didn't see what your question was/ what you wanted, so it might was unclear to them. (But sadly I'm out of votes for today, otherwise you and Rocket Hazmat would get an upV). — Rizier123, Jun 11 '15 at 21:29

score 3 · Accepted Answer · answered Jun 11 '15 at 21:32

This is the expected result. While '547533e683433' is not valid JSON, PHP can still "decode" it.

PHP implements a superset of JSON as specified in the original RFC 4627 - it will also encode and decode scalar types and NULL.

According to the docs for json_decode, PHP will decode single scalar values, not just arrays/objects.

In the case of '547533e683433', it's interpreted as an int when decoding (strings need to be in double quotes). 547533e683433 is read as 547533 x 10^683433 (see the docs for is_numeric), which is a huge number. PHP can't represent a number this big, so it gives you INF.

php json_decode returning infinite

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