做简单性能测试的更好方法

在比较操作性能时,我通常会这样做测试:

<?php
$w = 'world';
$start1 = microtime(true);
for($i=0;$i<10000;$i++)
    echo 'Hello ' . $w . '!';
$end1 = microtime(true);

$start2 = microtime(true);
for($i=0;$i<10000;$i++)
    echo "Hello $w!";
$end2 = microtime(true);

$start3 = microtime(true);
for($i=0;$i<10000;$i++)
    echo 'Hello ' + $w + '!';
$end3 = microtime(true);

echo "\n\n\n";
echo 'Concatination: ' . ($end1 - $start1) . "\nInline Var: " . ($end2 - $start2) . "\nAddition Operator: " . ($end3 - $start3);

有没有更好的方法来做这些测试,可能是更可靠的方法?似乎如果我多次运行相同的测试,我可以得到完全不同的结果,例如,我运行了以上几次,这就是我得到的结果。

Concatination: 0.057300090789795
Inline Var: 0.092978954315186
Addition Operator: 0.090532064437866

Concatination: 0.10458517074585
Inline Var: 0.075299978256226
Addition Operator: 0.039528131484985

Concatination: 0.063031911849976
Inline Var: 0.07781195640564
Addition Operator: 0.022316932678223

Concatination: 0.079019069671631
Inline Var: 0.030484914779663
Addition Operator: 0.096056938171387

Concatination: 0.077842950820923
Inline Var: 0.052779912948608
Addition Operator: 0.037421941757202

Concatination: 0.084203004837036
Inline Var: 0.013757944107056
Addition Operator: 0.074331045150757

Concatination: 0.027930021286011
Inline Var: 0.05648398399353
Addition Operator: 0.049610137939453

Concatination: 0.041821956634521
Inline Var: 0.047034978866577
Addition Operator: 0.062538862228394

Concatination: 0.0071420669555664
Inline Var: 0.066315889358521
Addition Operator: 0.004756927490234

Concatination: 0.088988065719604
Inline Var: 0.022722959518433
Addition Operator: 0.06276798248291

正如你在每次跑步中看到的那样,可能会有非常不同的结果。