Add json validator

[romkatsu]

Q	A
Is bugfix?	❌
New feature?	✔️
Breaks BC?	❌
Tests pass?	✔️
Fixed issues

• add json validator
• add trait
• edit composer.json

[romkatsu]

Json validator

[samdark]

👍

[armpogart]

Not sure if it really matters but I have a benchmark (if I implemented it correctly) that shows that using regex for validating json is faster, and the bigger the json, the more is the difference. For real world case the difference would not be visible at all, but another disadvantage of using json_decode for validation purposes here is that it will also consume memory by creating all that objects for the decoded data.

See benchmark

[armpogart]

Also json_decode successfully decodes any number (which you have check for), simple strings and boolean true (which also don't pass is_string check), which is not valid json in most languages. But simple strings still pass your validation, but they are not valid for javascript JSON.parse.

That's due to the fact that PHP implements a superset of JSON specified in RFC 7159 vs older standard that is implemented by javascript and majority: RFC 4267.

Also there is a newer revision of json standard: RFC 8259, which I doubt any language implemented at all.

[samdark]

@armpogart are you sure it is complete regex that validates JSON?

[armpogart]

@samdark The regex is from RFC 4267 section 6. I'll open another discussion (issue) with details posted here and references to all the data I got. There are also json validation test cases on json.org which can be used for json validator testing.

Anyways I'll post all the details in an issue reference it here. I think there are some points that need further discussion.

[samdark]

Alright. Overall benchmarks look good enough to try it.