php json_encode 参数常量
JSON_HEX_TAG => 1
JSON_HEX_AMP => 2
JSON_HEX_APOS => 4
JSON_HEX_QUOT => 8
JSON_FORCE_OBJECT => 16
JSON_NUMERIC_CHECK => 32
JSON_UNESCAPED_SLASHES => 64
JSON_PRETTY_PRINT => 128
JSON_UNESCAPED_UNICODE => 256
JSON_ERROR_DEPTH => 1
JSON_ERROR_STATE_MISMATCH => 2
JSON_ERROR_CTRL_CHAR => 3
JSON_ERROR_SYNTAX => 4
JSON_ERROR_UTF8 => 5
JSON_OBJECT_AS_ARRAY => 1
JSON_BIGINT_AS_STRING =>