PHP Array and ArrayObject

The basic type is array. This is a map of keys and values that can be written to, read from and accessed in a loop.

The ArrayObject is a class that you can extend to create objects that behave as if they were arrays. It implements methods like count and sort that enable you to treat an object like you would treat an array. It's part of the SPL (Standard PHP Library).

Typically you'd use array. You'll know when you need ArrayObject.

In term of performance, you won't notice a real difference between an array and a ArayObject.I run a simple test. The idea was to create arrays using array() and new ArrayObject, and fill them with an increasing number of values.

<?phpfor($i = 0; $i < 2; $i++){    $method = $i == 0 ? 'array' : 'ArrayObject';    for($j = 0; $j < 7 ; $j++){        for($k = 0; $k < 100; $k++){            $max    = pow(10,$j);            $array  = $method == 'array' ? array() : new ArrayObject;            $time   = explode(' ',microtime());            $sTime  = $time[0] + $time[1];            for($l = 0; $l < $max; $l++){                $array[] = 'foo ' . $i . ':' . $j . ':' . $k . ':' . $l;            }            $time  = explode(' ',microtime());            $eTime = $time[0] + $time[1];            $results[$method][$max][]    = $eTime - $sTime;        }    }}?>

Results

method             lines     average (µs)    difference between methods (µs)array                  1           2.470         -1.044array                 10           8.452         +0.315array                100          71.862        +10.719array              1,000         773.826       +141.962array             10,000       7,868.731       -675.359array            100,000      76,954.625    -17,665.510array          1,000,000     801,509.550    -84,356.148ArrayObject            1           3.514         +1.044ArrayObject           10           8.137         -0.315ArrayObject          100          61.142        -10.719ArrayObject        1,000         631.864       -141.962ArrayObject       10,000       8,544.090       +675.359ArrayObject      100,000      94,620.135    +17,665.510ArrayObject    1,000,000     885,865.698    +84,356.148

The average is the average time of the 100 tests for each method and each number of lines.The difference between methods is quite insignificant (84 microseconds when you deal with a million rows...)

I've run this test many times, and because the differences are always a question of microseconds, sometimes a method is more efficient during one test, then less efficient during the next test...

The choice will depend of your needs:

• if you deal with simple arrays, and do a loop like foreach() or calculate an average, an array is quite enough,
• if you need more complex iterations, sorting, filtering, ... it's easier to expand the ArrayObject class with your own iterator, methods...

arrayObject is mostly useful when serialization is needed.

Also you can create your own collection class by extending arrayObject. Then you can serialize your class object to transfer data.

for simple and usual operation array is more prefferable than arrayObject.