This question already has an answer here:
I have a JSON file, but I can't decode it like any other JSON file. Where am I making a mistake?
$jsonData = '[[[],[{"file_id":"2_U_3","sub_file_id":"2_U_3_1","option_file":[0,3.44827586207],"file_votes":1}],[],[],[],[]],{}]';
$jsonDec = json_decode($jsonData, TRUE);
echo $jsonDec["file_id"] . " = " . $jsonDec["option_file"][2];
Result: empty screen
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