Comparing CPU time and memory usage between classes and arrays.

bench1.php

<?php
$i = 0;
$x = [];
$start = microtime( true );
do {
    $x[] = array( "firstname" => "Patrick", "lastname" => "Allaert" );
    ++$i;
} while ( $i < 500000 );
echo microtime( true ) - $start, "\n", memory_get_peak_usage(), "\n";

bench2.php

<?php
$i = 0;
$x = [];
class person {
    public $firstname;
    public $lastname;
}
$start = microtime( true );
do {
    $p = new person;
    $p->firstname = "Patrick";
    $p->lastname = "Allaert";
    $x[] = $p;
    ++$i;
} while ( $i < 500000 );
echo microtime( true ) - $start, "\n", memory_get_peak_usage(), "\n";

bench3.php

<?php
$i = 0;
$x = [];
class person {
    public $firstname;
    public $lastname;
    
    public function __construct( $firstname, $lastname ) {
        $this->firstname = $firstname;
        $this->lastname = $lastname;
    }
}
$start = microtime( true );
do {
    $x[] = new person( "Patrick", "Allaert" );
    ++$i;
} while ( $i < 500000 );
echo microtime( true ) - $start, "\n", memory_get_peak_usage(), "\n";

Results.txt

PHP 5.4:
========

$ php54 bench1.php 
0.36937880516052
292432712

$ php54 bench2.php 
0.47057294845581
193929016

$ php54 bench3.php 
0.79254007339478
193944896

PHP 5.3:
========

$ php53 bench1.php 
1.0838158130646
684949896

$ php53 bench2.php 
1.8599081039429
774477240

$ php53 bench3.php 
2.2024641036987
774479960

Arrays takes much more space than equivalent struct classes but are slighly faster in *PHP 5.4*.