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有什么方法可以更快地提取字符串?

pattern-matching string algorithm php

Renato Aquino · 技术社区 · 16 年前

我需要提取HTTP请求的虚拟主机名。

有没有更快的方法?

$hostname = "alphabeta.gama.com";

$iteractions = 100000;

//While Test

$time_start = microtime(true);
for($i=0;$i < $iteractions; $i++){
    $vhost = "";
    while(($i < 20) && ($hostname{$i} != '.')) $vhost .= $hostname{$i++};
}

$time_end = microtime(true);
$timewhile = $time_end - $time_start;

//Regexp Test
$time_start = microtime(true);
for($i=0; $i<$iteractions; $i++){
    $vhost = "";
    preg_match("/([A-Za-z])*/", $hostname ,$vals);
    $vhost = $vals[0];
}
$time_end = microtime(true);
$timeregex = $time_end - $time_start;

//Substring Test
$time_start = microtime(true);
for($i=0;$i<$iteractions;$i++){
    $vhost = "";
    $vhost = substr($hostname,0,strpos($hostname,'.'));
}
$time_end = microtime(true);
$timesubstr = $time_end - $time_start;

//Explode Test
$time_start = microtime(true);
for($i=0;$i<$iteractions;$i++){
    $vhost = "";
    list($vhost) = explode(".",$hostname);
}
$time_end = microtime(true);
$timeexplode = $time_end - $time_start;

//Strreplace Test. Must have the final part of the string fixed.
$time_start = microtime(true);
for($i=0;$i<$iteractions;$i++){
    $vhost = "";
    $vhost = str_replace(".gama.com","",$hostname);
}
$time_end = microtime(true);
$timereplace = $time_end - $time_start;

echo "While   :".$timewhile."\n";
echo "Regex   :".$timeregex."\n";
echo "Substr  :".$timesubstr."\n";
echo "Explode :".$timeexplode."\n";
echo "Replace :".$timereplace."\n";

因此,时间安排:

While   :0.0886390209198
Regex   :1.22981309891
Substr  :0.338994979858
Explode :0.450794935226
Replace :0.33411693573

3 回复 | 直到 16 年前

Ville Laurikari 16 年前

您可以尝试使用strtok()函数:

$vhost = strtok($hostname, ".")

它比while循环的正确版本快,

Alex 16 年前

我会用substr()的方法。

$vhost = substr($host, 0, strstr($host, "."));

我真的不认为分割字符串的方式会影响任何实际程序的性能。100000次迭代是相当大的…;-)

Kris 16 年前

<?php
$iterations = 100000;
$fullhost = 'subdomain.domain.tld';

$start = microtime(true);

for($i = 0; $i < $iterations; $i++) 
{
    $vhost = substr($fullhost, 0, strpos($fullhost, '.'));
}

$total = microtime(true) - $start;
printf( 'extracted %s from %s %d times in %s seconds', $vhost, $fullhost, $iterations, number_format($total,5));
?>

在0.44695秒内从subdomain.domain.tld提取子域100000次

但这是在编码视频时发生的,所以在更好的情况下它可能会更快。

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