JSON: why are forward slashes escaped?

Question

The reason for this \"escapes\" me.

JSON escapes the forward slash, so a hash {a: \"a/b/c\"} is serialized as {\"a\":\"a\\/b\\/c\"} instead

Answer 1

Ugly PHP!

The JSON_UNESCAPED_UNICODE|JSON_UNESCAPED_SLASHES must be default, not an (strange) option... How to say it to php-developers?

The default MUST be the most frequent use, and the (current) most widely used standards as UTF8. How many PHP-code fragments in the Github or other place need this exoctic "embedded in HTML" feature?