The SplFixedArray class

(PHP 5 >= 5.3.0)

简介

The SplFixedArray class provides the main functionalities of array. The main differences between a SplFixedArray and a normal PHP array is that the SplFixedArray is of fixed length and allows only integers within the range as indexes. The advantage is that it allows a faster array implementation.

类摘要

SplFixedArray implements Iterator , ArrayAccess , Countable {

/* 方法 */

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 )

public void __wakeup ( void )

}

范例

Example #1 SplFixedArray usage example


<?php
// Initialize the array with a fixed length
$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"

// Increase the size of the array to 10
$array->setSize(10);

$array[9] = "asdf";

// Shrink the array to a size of 2
$array->setSize(2);

// The following lines throw a RuntimeException: Index invalid or out of range
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";
}
?>

以上例程会输出：

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

SplFixedArray::__construct — Constructs a new fixed array
SplFixedArray::count — Returns the size of the array
SplFixedArray::current — Return current array entry
SplFixedArray::fromArray — Import a PHP array in a SplFixedArray instance
SplFixedArray::getSize — Gets the size of the array
SplFixedArray::key — Return current array index
SplFixedArray::next — Move to next entry
SplFixedArray::offsetExists — Returns whether the requested index exists
SplFixedArray::offsetGet — Returns the value at the specified index
SplFixedArray::offsetSet — Sets a new value at a specified index
SplFixedArray::offsetUnset — Unsets the value at the specified $index
SplFixedArray::rewind — Rewind iterator back to the start
SplFixedArray::setSize — Change the size of an array
SplFixedArray::toArray — Returns a PHP array from the fixed array
SplFixedArray::valid — Check whether the array contains more elements
SplFixedArray::__wakeup — Reinitialises the array after being unserialised

用户评论:

artaxerxes (2012-11-13 04:41:10)

As the documentation says, SplFixedArray is meant to be *faster* than array. Do not blindly believe other people's benchmarks, and beextra careful with the user comments on php.net. For instance, nairbv's benchmark code is completely wrong. Among other errors, it intends to increase the size of the arrays, but always initialize a 20 elements SplFixedArray. On a PHP 5.4 64 bits linux server, I found SplFixedArray to be always faster than array(). * small data (1,000): * write: SplFixedArray is 15 % faster * read: SplFixedArray is 5 % faster * larger data (512,000): * write: SplFixedArray is 33 % faster * read: SplFixedArray is 10 % faster

alex dot andrienko at gmail dot com (2010-11-15 02:13:15)

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 (2009-10-21 02:08:48)

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 (2009-07-14 11:07:21)

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

The SplFixedArray class

简介

类摘要

范例

Table of Contents

用户评论: