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PHP 函数执行效率的小比较_PHP

Jun 01, 2016 pm 12:17 PM
function effectiveness

就是把原来的数组中的数都“拆”成“单”位的。
下面是自己写的一个函数:
复制代码 代码如下:
function splitStrToArray_mine($array)
{
$new_array = array();
foreach($array as $value)
{
$value = (string)$value;
$len = strlen($value);
for($i = 0; $i array_push($new_array, $value{$i});
}
}
return $new_array;
}

测试了一下,还是可以执行的,如下调用:
复制代码 代码如下:
//测试数组
$data = array(12, 43, 87, 45, 98, 74, 83, 67, 12);
var_dump(splitStrToArray_mine($data));

输出结果为:
复制代码 代码如下:
array(18) {
[0]=>
string(1) "1"
[1]=>
string(1) "2"
[2]=>
string(1) "4"
[3]=>
string(1) "3"
[4]=>
string(1) "8"
[5]=>
string(1) "7"
[6]=>
string(1) "4"
[7]=>
string(1) "5"
[8]=>
string(1) "9"
[9]=>
string(1) "8"
[10]=>
string(1) "7"
[11]=>
string(1) "4"
[12]=>
string(1) "8"
[13]=>
string(1) "3"
[14]=>
string(1) "6"
[15]=>
string(1) "7"
[16]=>
string(1) "1"
[17]=>
string(1) "2"
}

虽然执行的不错,但是看看标准答案就会让你大吃一惊的,函数中就一句话,如下:
复制代码 代码如下:
//标准函数
function splitStrToArray($array)
{
return str_split(implode("", $array));
}

于是写了脚本来测试自己的和标准的函数的运行效率差距,里面有一个 microtime_float() 函数用来提供精确时间的支持:
复制代码 代码如下:
//测量时间的函数
function microtime_float()
{
list($usec, $sec) = explode(" ", microtime());
return ((float)$usec + (float)$sec);
}
//自定义函数
function splitStrToArray_mine($array)
{
$new_array = array();
foreach($array as $value)
{
$value = (string)$value;
$len = strlen($value);
for($i = 0; $i array_push($new_array, $value{$i});
}
}
return $new_array;
}
//标准函数
function splitStrToArray($array)
{
return str_split(implode("", $array));
}
//测试数组
$data = array(12, 43, 87, 45, 98, 74, 83, 67, 12);
//开始测试
$mine_start = microtime_float();
splitStrToArray_mine($data);
$mine_end = microtime_float();
//标准函数调用
$sta_start = microtime_float();
splitStrToArray($data);
$sta_end = microtime_float();
echo "自己的函数调用运行时间为:" . (float)($mine_end - $mine_start) . " S
";
echo "标准的函数调用运行时间为:" . (float)($sta_end - $sta_start) . " S
";
$multiple = (int)((float)($mine_end - $mine_start) / (float)($sta_end - $sta_start));
echo "前者是后者的:" . $multiple . " 倍!";

来看看输出结果:
自己的函数调用运行时间为:9.3936920166E-005 S
标准的函数调用运行时间为:2.69412994385E-005 S
前者是后者的:3 倍!
多次刷新页面的话,可以发现标准函数的执行效率基本上是自己的函数的 3 倍!当然,标准的函数中使用了 PHP 的内置函数: str_split(),implode(),所以要比自己写函数快得多,对 str_split() 函数没有印象?来看看手册解释:
str_split -- Convert a string to an array(将一个字符串转换成数组)
函数描述:
array str_split ( string string [, int split_length] )
复制代码 代码如下:
Converts a string to an array. If the optional split_length parameter is specified, the returned array will be broken down into chunks with each being split_length in length, otherwise each chunk will be one character in length.
FALSE is returned if split_length is less than 1. If the split_length length exceeds the length of string, the entire string is returned as the first (and only) array element.

例 1. Example uses of str_split()
复制代码 代码如下:
$str = "Hello Friend";
$arr1 = str_split($str);
$arr2 = str_split($str, 3);
print_r($arr1);
print_r($arr2);
?>

Output may look like:
复制代码 代码如下:
Array
(
[0] => H
[1] => e
[2] => l
[3] => l
[4] => o
[5] =>
[6] => F
[7] => r
[8] => i
[9] => e
[10] => n
[11] => d
)
Array
(
[0] => Hel
[1] => lo
[2] => Fri
[3] => end
)

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