从多维数组中提取数组

So here is my array:

array(1) { [0]=> string(79) "{"form_array":{"element1":"value1","element2":"value2","element3":"value3"}}" }

How can I extract "form_array" as an array?

You actually have just a simple array with one element, which is a string, that seems to be JSON encoded. To get its data, you may use the following:

// get the string
$data = $array[0];

// decode the content
$data = json_decode( $data, true );

// get the sub array
$data = $data['form_array'];

_{The steps may of course be simplified into a single row. I just separated them for readability and clarity.}

You can try

$array = json_decode($array[0]);
$formArray = $array->form_array;

If you have posted the result of var_dump(arrayname), then this code only will help you

$data = $data['form_array'];

else you can go with Sirko's anser