Get a multidimensional array key?

For example, I have multidimensional array as below:

$array = array (
  0 =>
    array (
      'id' => '9',
      'gallery_id' => '2',
      'picture' => '56475832.jpg'
    ),
  1 =>
    array (
      'id' => '8',
      'gallery_id' => '2',
      'picture' => '20083622.jpg'
    ),
  2 =>
    array (
      'id' => '7',
      'gallery_id' => '2',
      'picture' => '89001465.jpg'
    ),
  3 =>
    array (
      'id' => '6',
      'gallery_id' => '2',
      'picture' => '47360232.jpg'
    ),
  4 =>
    array (
      'id' => '5',
      'gallery_id' => '2',
      'picture' => '4876713.jpg'
    ),
  5 =>
    array (
      'id' => '4',
      'gallery_id' => '2',
      'picture' => '5447392.jpg'
    ),
  6 =>
    array (
      'id' => '3',
      'gallery_id' => '2',
      'picture' => '95117187.jpg'
    )
);

How can I get key of array(0,1,2,3,4,5,6)?

I have tried a lot of examples, but nothing has worked for me.


This is quite simple, you just need to use array_keys():

$keys = array_keys($array);

See it working

EDIT For your search task, this function should do the job:

function array_search_inner ($array, $attr, $val, $strict = FALSE) {
  // Error is input array is not an array
  if (!is_array($array)) return FALSE;
  // Loop the array
  foreach ($array as $key => $inner) {
    // Error if inner item is not an array (you may want to remove this line)
    if (!is_array($inner)) return FALSE;
    // Skip entries where search key is not present
    if (!isset($inner[$attr])) continue;
    if ($strict) {
      // Strict typing
      if ($inner[$attr] === $val) return $key;
    } else {
      // Loose typing
      if ($inner[$attr] == $val) return $key;
    }
  }
  // We didn't find it
  return NULL;
}

// Example usage
$key = array_search_inner($array, 'id', 9);

The fourth parameter $strict, if TRUE, will use strict type comparisons. So 9 will not work, you would have to pass '9', since the values are stored as strings. Returns the key of the first occurence of a match, NULL if the value is not found, or FALSE on error. make sure to use a strict comparison on the return value, since 0, NULL and FALSE are all possible return values and they will all evaluate to 0 if using loose integer comparisons.