json_encode adding lots of decimal digits

You should configure 'precision' and 'serialize_precision' params.

precision = 14
serialize_precision = -1

Test case:

php -r 'var_dump(json_encode([1002.31, 2002.42]));'
string(39) "[1002.3099999999999,2002.4200000000001]"

php -r 'ini_set("precision", 14); ini_set("serialize_precision", -1); var_dump(json_encode([1002.31, 2002.42]));'
string(17) "[1002.31,2002.42]"

This is occurring due to the inaccuracy of floating points as they cannot be directly represented in binary. A site that explains some of this is here.

A quick fix may be to pass them through as strings and convert them back at the other end, or multiply them up to be integers and then again convert back at the other end.

Sadly there is no real 'fix' for this behaviour.

Quick solution from me. Add this line to your PHP code.

ini_set('serialize_precision','-1');