Question

I have an array that has a list of PID, Email and Client in a comma delimited array. I was wondering if there’s a way to parse the input array and generate a new array that has “Email” as the key and all unique PIDs for that email. Since the input array can have thousands of elements, I was wondering about the fastest approach.

Ex: Input Array (PID, Email, Client)
--------------------------------------
Array ( 
[0] => 10, [e-mail],Gmail 
[1] => 11, [e-mail],Gmail
[2] => 12, [e-mail],Gmail 
[3] => 13, [e-mail],Gmail
[4] => 14, [e-mail],Gmail 
[5] => 15, [e-mail],Gmail
)


Ex: Output Array (with Email as the key):
---------------------------------------------
Array (
[[e-mail]] => (
                   [0] => 10
               [1] => 12
          ),
[[e-mail]] => (
               [0] => 11
               [1] => 13
               [2] => 15
          ),
[[e-mail]] => (
               [0] => 14
          )
)

Thanks

Answer 1

// $input holds your initial array:
// $ouput is output...
$output = array();
foreach ($input as $arr) {
  // Explode the comma-delimited lines into 3 vars
  list($pid, $email, $client) = explode(",", $arr);
  // Initialize a new array for the Email key if it doesn't exist
  if (!isset($output[$email])) $output[$email] = array();
  // Append the PID to the Email key
  $output[$email][] = $pid;
}