php: how to get associative array key from numeric index?

$array = array( 'one' =>'value', 'two' => 'value2' );

$allKeys = array_keys($array);
echo $allKeys[0];

Which will output:

one

You don't. Your array doesn't have a key [1]. You could:

  • Make a new array, which contains the keys:

    $newArray = array_keys($array);
    echo $newArray[0];
    

    But the value "one" is at $newArray[0], not [1].
    A shortcut would be:

    echo current(array_keys($array));
    
  • Get the first key of the array:

     reset($array);
     echo key($array);
    
  • Get the key corresponding to the value "value":

    echo array_search('value', $array);
    

This all depends on what it is exactly you want to do. The fact is, [1] doesn't correspond to "one" any which way you turn it.