Took 0.164692 seconds for array[]
Took 0.395778 seconds for array_push

As you can see array_push is more than twice as slow. Here are the reasons. Array_push is a function call, Function calls are always slower. Array_push takes mixed parameters, parameter checking is always slower. Also array[] just looks cleaner and is less to type.

Tips: Always pre-intialize your variables and don't use mixed types even though you can.

$time_start = microtime(true);
 
$myArray = array();
 
for ( $i = 0; $i < 100000; ++$i )
{
   $myArray[] = $i;
   $myArray[] = 'test a string';
}
 
$time_end = microtime(true);
printf("Took %f seconds for array[]\n", $time_end - $time_start);
 
$time_start = microtime(true);
 
$myArray = array();
 
for ( $i = 0; $i < 100000; ++$i )
{
   array_push($myArray, $i);
   array_push($myArray, 'test a string');
}
 
$time_end = microtime(true);
printf("Took %f seconds for array_push\n", $time_end - $time_start);