add to existing array

[ggalan]

i am adding to an existing array and it seems to work like this

$arr[] .= 'a';
$arr[] .= 'b';
$arr[] .= 'c';

but if i wanted it written in 1 line like this, what is the correct way?
this doesnt seem to work

$arr[] .= array('a', 'b', 'c');

re:
array_push seems to work

array_push($arr, 'a', 'b', 'c', 'd');

[traq]

i am adding to an existing array and it seems to work like this

$arr[] .= 'a';
$arr[] .= 'b';
$arr[] .= 'c';

but if i wanted it written in 1 line like this, what is the correct way?
this doesnt seem to work

First: you shouldn't be using the concatenation assignment ( .= ).
Once that's corrected, both methods will work, but will provide different results:

<?php
$array1[] = 'a';
$array1[] = 'b';
$array1[] = 'c';
var_dump( $array1 );
/* output:
array(3) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
}
BTW, this:
    $arr = array();
    array_push($arr, 'a','b','c' );
has _exactly_ the same result as the method above (but is less efficient)
*/

$array2[] = array( 'a','b','c' );
var_dump( $array2 );
/* output:
array(1) {
  [0]=>
  array(3) {
    [0]=>
    string(1) "a"
    [1]=>
    string(1) "b"
    [2]=>
    string(1) "c"
  }
}
*/

I suspect what you want, however, is a simple array construct:

<?php
$array = array( 'a','b','c' );
var_dump( $array );
/* output:
array(3) {
  [0]=>
  string(1) "a"
  [1]=>
  string(1) "b"
  [2]=>
  string(1) "c"
}
*/