[edit] Last updated: Fri, 25 May 2012

La classe SplFixedArray

(PHP 5 >= 5.3.0)

Introduction

La classe SplFixedArray fournit les fonctionnalités principales d'un tableau. La différence majeure entre un objet SplFixedArray et un tableau standard de PHP est que SplFixedArray est de taille fixe, et n'utilise que des entier dans ses index. L'avantage est alors qu'il est plus rapide que les tableaux.

Synopsis de la classe

SplFixedArray implements Iterator , ArrayAccess , Countable {

/* Méthodes */

public __construct ([ int $size = 0 ] )

public int count ( void )

public mixed current ( void )

public static SplFixedArray fromArray ( array $array [, bool $save_indexes = true ] )

public int getSize ( void )

public int key ( void )

public void next ( void )

public bool offsetExists ( int $index )

public mixed offsetGet ( int $index )

public void offsetSet ( int $index , mixed $newval )

public void offsetUnset ( int $index )

public void rewind ( void )

public int setSize ( int $size )

public array toArray ( void )

public bool valid ( void )

}

Exemples

Exemple #1 Exemple avec SplFixedArray


<?php
// Initialisation d'un tableau avec une taille fixe
$array = new SplFixedArray(5);

$array[1] = 2;
$array[4] = "foo";

var_dump($array[0]); // NULL
var_dump($array[1]); // int(2)

var_dump($array["4"]); // string(3) "foo"

// Augmentation de la taille à 10
$array->setSize(10);

$array[9] = "asdf";

// Réduction de taille de 2
$array->setSize(2);

// Les lignes suivantes émettent une RuntimeException : index invalide ou hors de l'intervalle
try {
    var_dump($array["non-numeric"]);
} catch(RuntimeException $re) {
    echo "RuntimeException : ".$re->getMessage()."\n";
}

try {
    var_dump($array[-1]);
} catch(RuntimeException $re) {
    echo "RuntimeException : ".$re->getMessage()."\n";
}

try {
    var_dump($array[5]);
} catch(RuntimeException $re) {
    echo "RuntimeException : ".$re->getMessage()."\n";
}
?>

L'exemple ci-dessus va afficher :

NULL
int(2)
string(3) "foo"
RuntimeException: Index invalid or out of range
RuntimeException: Index invalid or out of range
RuntimeException: Index invalid or out of range

Sommaire

SplFixedArray::__construct — Construit un nouveau SplFixedArray
SplFixedArray::count — Retourne la taille du tableau à taille fixe
SplFixedArray::current — Lit l'élément courant du tableau à taille fixe
SplFixedArray::fromArray — Importe un tableau PHP dans un tableau à taille fixe
SplFixedArray::getSize — Lit la taille du tableau à taille fixe
SplFixedArray::key — Retourne l'index de la position courante
SplFixedArray::next — Déplace l'itérateur à l'élément suivant
SplFixedArray::offsetExists — Vérifie si l'index demandé existe
SplFixedArray::offsetGet — Retourne la valeur à l'index donné
SplFixedArray::offsetSet — Affecte une valeur à un index donné
SplFixedArray::offsetUnset — Détruit l'élément à un index donné
SplFixedArray::rewind — Remet l'itérateur au début du tableau à taille fixe
SplFixedArray::setSize — Change la taille d'un tableau à taille fixe
SplFixedArray::toArray — Retourne un tableau PHP à partir d'un tableau à taille fixe
SplFixedArray::valid — Vérifie si le tableau contient encore un élément

SplFixedArray::__construct

SplPriorityQueue::valid

[edit] Last updated: Fri, 25 May 2012

add a note User Contributed Notes SplFixedArray

alex dot andrienko at gmail dot com 15-Nov-2010 02:13


Memory footprint of splFixedArray is about 37% of a regular "array" of the same size. 

I was hoping for more, but that's also significant, and that's where you should expect to see difference, not in "performance".

nairbv AT yahoo DOT com 21-Oct-2009 02:08


Though, object creation overhead means this method is slower for small arrays.



for example, if the other posters benchmark script is changed to a more realistic:



<?php

$elements = 20;

for($size = 1000; $size < 50000000; $size *= 2) {

    echo PHP_EOL . "Testing size: $size" . PHP_EOL;

    for($s = microtime(true), $i = 0; $i < $size; $i++) {

        for($j=0,$container=array();$j < $elements; $j++ ) {

            $container[$i] = NULL;

        }

    }

    echo "Array(): " . (microtime(true) - $s) . PHP_EOL;



    for($s = microtime(true), $i = 0; $i < $size; $i++) {

        for( $j=0,$container=new SplFixedArray($elements);$j<$elements;$j++) {

            $container[$i] = NULL;

        }

    }

    echo "SplArray(): " . (microtime(true) - $s) . PHP_EOL;

}



we get:



Testing size: 1000

Array(): 0.0030221939086914

SplArray(): 0.0041899681091309



Testing size: 2000

Array(): 0.0060598850250244

SplArray(): 0.0083701610565186



Testing size: 4000

Array(): 0.012003898620605

SplArray(): 0.016681909561157



Testing size: 8000

Array(): 0.024173021316528

SplArray(): 0.033347129821777



Testing size: 16000

Array(): 0.048118829727173

SplArray(): 0.066897869110107



Testing size: 32000

Array(): 0.096546173095703

SplArray(): 0.13370203971863



Testing size: 64000

Array(): 0.1932430267334

SplArray(): 0.26755595207214



Testing size: 128000

Array(): 0.38473010063171

SplArray(): 0.5374698638916



Testing size: 256000

Array(): 0.77228307723999

SplArray(): 1.0708079338074



Testing size: 512000

Array(): 1.5438990592957

SplArray(): 2.1406710147858



Testing size: 1024000

Array(): 3.0910761356354

SplArray(): 4.3108429908752



Testing size: 2048000

Array(): 6.1561989784241

SplArray(): 8.612802028656



......

chrisstocktonaz at gmail dot com 14-Jul-2009 11:07


Note, that this is considerably faster and should be used when the size of the array is known. Here are some very basic bench marks:





<?php


for($size = 1000; $size < 50000000; $size *= 2) {


    echo PHP_EOL . "Testing size: $size" . PHP_EOL;


    for($s = microtime(true), $container = Array(), $i = 0; $i < $size; $i++) $container[$i] = NULL;


    echo "Array(): " . (microtime(true) - $s) . PHP_EOL;





    for($s = microtime(true), $container = new SplFixedArray($size), $i = 0; $i < $size; $i++) $container[$i] = NULL;


    echo "SplArray(): " . (microtime(true) - $s) . PHP_EOL;


}


?>





OUTPUT


Testing size: 1000


Array(): 0.00046396255493164


SplArray(): 0.00023293495178223





Testing size: 2000


Array(): 0.00057101249694824


SplArray(): 0.0003058910369873





Testing size: 4000


Array(): 0.0015869140625


SplArray(): 0.00086307525634766





Testing size: 8000


Array(): 0.0024251937866211


SplArray(): 0.00211501121521





Testing size: 16000


Array(): 0.0057680606842041


SplArray(): 0.0041120052337646





Testing size: 32000


Array(): 0.011334896087646


SplArray(): 0.007631778717041





Testing size: 64000


Array(): 0.021990060806274


SplArray(): 0.013560056686401





Testing size: 128000


Array(): 0.053267002105713


SplArray(): 0.030976057052612





Testing size: 256000


Array(): 0.10280108451843


SplArray(): 0.056283950805664





Testing size: 512000


Array(): 0.20657992362976


SplArray(): 0.11510300636292





Testing size: 1024000


Array(): 0.4138810634613


SplArray(): 0.21826505661011





Testing size: 2048000


Array(): 0.85640096664429


SplArray(): 0.46247816085815





Testing size: 4096000


Array(): 1.7242450714111


SplArray(): 0.95304894447327





Testing size: 8192000


Array(): 3.448086977005


SplArray(): 1.96746301651

add a note