Improve cURL response parsing for more stable body extraction

[sunlix]

During debugging I found that my cURL response does not match the expected shape by the current body parsing logic.

cuRL response string

HTTP/1.0 200 Connection established

HTTP/2 200
etag: "40eb12e1db3bd316a20e421579eb0c9319c33029"
content-type: application/json; charset=UTF-8
vary: Origin
vary: Accept-Encoding
cross-origin-resource-policy: cross-origin
x-app-usage: {"call_volume":2,"cpu_time":0}
instagram-api-version: v13.0
access-control-allow-origin: *
strict-transport-security: max-age=15552000
pragma: no-cache
cache-control: private, no-cache, no-store, must-revalidate
expires: Sat, 01 Jan 2000 00:00:00 GMT
x-fb-request-id: A3EagUez3D06PfR2W7NCLRo
x-fb-trace-id: HjzEzEg1A1S
x-fb-rev: 1006485593
x-fb-debug: ey8syhgmGO8S8cxwdQ5TguFJJNvNleHMzmgtAyqg29Fu78JsqDEEjeE24i0ZK9paxiv8amEK9ieEFTptkhx+0w==
date: Fri, 28 Oct 2022 06:43:12 GMT
priority: u=3,i
x-fb-trip-id: 1814657579

{"data":[],"paging":{}}

after trying to explode the json data from the cURL response string.

$headerContent

HTTP/1.0 200 Connection established

$jsonData

HTTP/2 200
etag: "40eb12e1db3bd316a20e421579eb0c9319c33029"
content-type: application/json; charset=UTF-8
vary: Origin
vary: Accept-Encoding
cross-origin-resource-policy: cross-origin
x-app-usage: {"call_volume":2,"cpu_time":0}
instagram-api-version: v13.0
access-control-allow-origin: *
strict-transport-security: max-age=15552000
pragma: no-cache
cache-control: private, no-cache, no-store, must-revalidate
expires: Sat, 01 Jan 2000 00:00:00 GMT
x-fb-request-id: A3EagUez3D06PfR2W7NCLRo
x-fb-trace-id: HjzEzEg1A1S
x-fb-rev: 1006485593
x-fb-debug: ey8syhgmGO8S8cxwdQ5TguFJJNvNleHMzmgtAyqg29Fu78JsqDEEjeE24i0ZK9paxiv8amEK9ieEFTptkhx+0w==
date: Fri, 28 Oct 2022 06:43:12 GMT
priority: u=3,i
x-fb-trip-id: 1814657579

{"data":[],"paging":{}}

$jsonData has no valid json string which ca be decoded. So json_decode returns null