I benchmarked it for you: CodePad
Your intuition on this was correct!
$test=array();
for($run=0; $run<1000; $run++)
$test[]=rand(0,100);
$time=microtime(true);
for($run=0; $run<100; $run++)
$out=array_unique($test);
$time=microtime(true)-$time;
echo 'Array Unique: '.$time."\n";
$time=microtime(true);
for($run=0; $run<100; $run++)
$out=array_keys(array_flip($test));
$time=microtime(true)-$time;
echo 'Keys Flip: '.$time."\n";
$time=microtime(true);
for($run=0; $run<100; $run++)
$out=array_flip(array_flip($test));
$time=microtime(true)-$time;
echo 'Flip Flip: '.$time."\n";
Output:
Array Unique: 1.1829199790955
Keys Flip: 0.0084578990936279
Flip Flip: 0.0083951950073242
Note that array_keys(array_flip($array))
will give a new key values in order, which in many cases may be what you want (identical except much faster to array_values(array_unique($array))
), whereas array_flip(array_flip($array))
is identical (except much faster) to array_unique($array)
where the keys remain the same.