php json multidimensional arrays

Question

I have some confusion about why the following code does not work:

$data_set = array();
for($i=1; $i<=3; $i++)
{
  $data_val = array($i, $i*2);
  $data_set[] = $data_val;
}

echo json_encode($data_set);

What I expect is something like

[ [1,2], [2,4], [3,6] ]

What I get is an empty string.

But, If I do this

$data_set = array();
for($i=1; $i<=3; $i++)
{
  $data_val = array($i, $i*2);
  $data_set[] = json_encode($data_val);
}

echo json_encode($data_set);

I get something like this:

[ "[1,2]", "[2,4]", "[3,6]" ]

So, it seems like deeper Arrays do not work. What am I missing?

I tried running your first example and it gave me the expected result. i.e. [[1,2],[2,4],[3,6]] — Drumbeg, Jun 11 at 19:59
Can you do var_dump($data_set); instead? Your code works: 3v4l.org/AiL2U — Halcyon, Jun 11 at 20:00

crafter · Answer 1 · 2014-06-11 20:34:27Z

up vote 0 down vote

There is no reason to convert the elements of the array, then convert the entire

$data_set = array();
for($i=1; $i<=3; $i++)
{
  $data_set[] = array($i, $i*2);
}

echo json_encode($data_set);

answered Jun 11 at 20:34

crafter
2,5041920

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