PHP配列から重複した値を削除するにはどうすればよいですか?

array_unique(array)

<?php
$a1=array("a"=>"red","b"=>"green","c"=>"red");
$a2=array("1"=>"Cat","2"=>"Dog","3"=>"Cat","4"=>"rabbit");
var_dump(array_unique($a1));
var_dump(array_unique($a2));
?>

array (size=2)
  'a' => string 'red' (length=3)
  'b' => string 'green' (length=5)
array (size=3)
  1 => string 'Cat' (length=3)
  2 => string 'Dog' (length=3)
  4 => string 'rabbit' (length=6)

<?php
$result1 = array("a" => "green", "red", "b" => "green", "blue", "red");
var_dump($result1);
$result2 = array_unique($result1);
var_dump($result2);
?>

array (size=5)
  'a' => string 'green' (length=5)
  0 => string 'red' (length=3)
  'b' => string 'green' (length=5)
  1 => string 'blue' (length=4)
  2 => string 'red' (length=3)
array (size=3)
  'a' => string 'green' (length=5)
  0 => string 'red' (length=3)
  1 => string 'blue' (length=4)