如何检索JSON的值字符串并在PHP中内爆？

I need to retrieve the "data" value of my JSON and implode it.

MySQL ('wave' column)

{"sample_rate":44100,"samples_per_pixel":4410,"bits":8,"length":2668,"data":[0.13,0.19,0.15,0.11,0.13,0.13,0.24,0.35]}

So I tried:

PHP

$json = $row['wave'];
$json_array = json_decode($json);
$json_wave = implode(',', $json_array->data);

But I got this warning:

Warning:  implode(): Invalid arguments passed in ...

How can I implode the data value without encounter in that warning?