in_array vs strpos for performance in php

Question

I am logging in users via windows authentication and then storing that user's rights in a session variable. I use a delimited method of rights storage in a database i.e:

$rights //retrieved from database 
= 'read,edit,delete,admin'

so my question is should I;

//generate variable
$_SESSION['userrights'] = $rights ($rights is retrieved from database)

//use strpos to find if right is allowed
if (strpos($_SESSION['userrights'],"admin") !== false) { // do the function }

OR

//make array of rights
$_SESSION['userrights'] = explode(',',$rights)

//use in_array to find if right is allowed
if (in_array("admin",$_SESSION['userrights'])) { // do the function }

Bit of a OCD question as I presume the difference will be pretty much negligible for what I am doing but which would be the faster (use less resources) method?

Any answers appreciated except ones that insult my method of rights storage!

Answer 1

As I often work with large datasets, I'd go with isset or !empty on an associative array and check for the key, like @Barmar suggests. Here is a quick 1M benchmark on an Intel® Core™ i3-540 (3.06 GHz)

$test = array("read", "edit", "delete", "admin");

echo "<pre>";

// --- strpos($rights,$test[$i%4]) ---

$rights = 'read,edit,delete,admin';
$mctime = microtime(true);
for($i=0; $i<=1000000; $i++) { if (strpos($rights,$test[$i%4]) !== false) { }}
echo '  strpos(... '.round(microtime(true)-$mctime,3)."s\n";

// --- in_array($test[$i%4],$rights) ---

$rights = array("read", "edit", "delete", "admin");
$mctime = microtime(true);
for($i=0; $i<=1000000; $i++) { if (in_array($test[$i%4],$rights)) { }}
echo 'in_array(... '.round(microtime(true)-$mctime,3)."s\n";

// --- !empty($rights[$test[$i%4]]) ---

$rights = array('read' => 1, 'edit' => 1, 'delete' => 1, 'admin' => 1);
$mctime = microtime(true);
for($i=0; $i<=1000000; $i++) { if (!empty($rights[$test[$i%4]])) { }}
echo '  !empty(... '.round(microtime(true)-$mctime,3)."s\n";

// --- isset($rights[$test[$i%4]]) ---

$rights = array('read' => 1, 'edit' => 1, 'delete' => 1, 'admin' => 1);
$mctime = microtime(true);
for($i=0; $i<=1000000; $i++) { if (isset($rights[$test[$i%4]])) { }}
echo '   isset(... '.round(microtime(true)-$mctime,3)."s\n\n";

echo "</pre>";

The winner is isset:

  strpos(... 0.393s
in_array(... 0.519s
  !empty(... 0.232s
   isset(... 0.209s