Implode two-dimensional array in PHP - php

Question

I have an array like:
Array
(
[0] => Array
(
[0] => a
[1] => b
)
[1] => Array
(
[0] => c
)
[2] => Array
(
[0] => d
[1] => e
[2] => f
)
)
I want to convert my array to a string like below:
$arrtostr = 'a,b,c,d,e,f';
I've used implode() function but it looks like it doesn't work on two-dimensional arrays.
What should I do?

Answer 1

Alternatively, you could use a container for that first, merge the contents, and in the end of having a flat one, then use implode():
$letters = array();
foreach ($array as $value) {
$letters = array_merge($letters, $value);
}
echo implode(', ', $letters);
Sample Output

Answer 2

Given your subject array:
$subject = array(
array('a', 'b'),
array('c'),
array('d', 'e', 'f'),
);
Two easy ways to get a "flattened" array are:
PHP 5.6.0 and above using the splat operator:
$flat = array_merge(...$subject);
Lower than PHP 5.6.0 using call_user_func_array():
$flat = call_user_func_array('array_merge', $subject);
Both of these give an array like:
$flat = array('a', 'b', 'c', 'd', 'e', 'f');
Then to get your string, just implode:
$string = implode(',', $flat);

Answer 3

You asked for a two-dimensional array, here's a function that will work for multidimensional array.
function implode_r($g, $p) {
return is_array($p) ?
implode($g, array_map(__FUNCTION__, array_fill(0, count($p), $g), $p)) :
$p;
}
I can flatten an array structure like so:
$multidimensional_array = array(
'This',
array(
'is',
array(
'a',
'test'
),
array(
'for',
'multidimensional',
array(
'array'
)
)
)
);
echo implode_r(',', $multidimensional_array);
The results is:
This,is,a,test,for, multidimensional,array