PHP variable reference and non-reference performance comparison

<?php

// PREVIEW：数据需要修改的就用引用，数据不需要修改的就用非引用

$arrayCount = 2000;

$cycleCount = 100000;

// 向函数传递参数并做修改

echo "向函数传递参数并做修改", PHP_EOL;

function ByVal($p){return $p[intval(count($p) / 2)] += 1;} 

function ByRef(&$p){return $p[intval(count($p) / 2)] += 1;}

$p = array_fill(0, $arrayCount, 1);

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $a = ByVal($p);

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByValFun: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $a = ByRef($p);

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRefFun: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL , PHP_EOL;

// END: 速度相近，内存引用胜出

// 向函数传递参数不做修改

echo "向函数传递参数不做修改", PHP_EOL;

function ByVal2($p){return $p[intval(count($p) / 2)];} 

function ByRef2(&$p){return $p[intval(count($p) / 2)];}

$p = array_fill(0, $arrayCount, 1);

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $a = ByVal2($p);

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByValFun: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $a = ByRef2($p);

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRefFun: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL , PHP_EOL;

// END: 传值性能大幅胜出，内存相近

// 变量赋值做修改

echo "变量赋值做修改", PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    $a = $p;

    $a[2] += 1;

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByVal: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    $a = &$p;

    $a[2] += 1;

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRef: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL , PHP_EOL;

// END 速度相近，引用略胜；内存引用大幅胜出

// 变量赋值不做修改

echo "变量赋值不做修改", PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    $a = $p;

    $b = $a[2];

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByVal: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    $a = &$p;

    $b = $a[2];

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRef: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL , PHP_EOL;

// END 速度相近，内存相近

// 数组内循环赋值修改数据

echo "数组内循环赋值修改数据", PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    foreach($p as $key => $val){

        $p[$key] += 1;

    }

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByKey: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    foreach($p as &$val){

        $val += 1;

    }

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRef: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL , PHP_EOL;

// END: 引用胜出

// 数组内循环赋值不修改数据

echo "数组内循环赋值不修改数据", PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    foreach($p as $key => $val){

        $b = $val;

    }

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByKey: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

$start = microtime(true);

$startMem = Memory_get_usage();

for($i = 0; $i < $cycleCount; $i += 1){

    $p = array_fill(0, $arrayCount, 1);

    foreach($p as &$val){

        $b = $val;

    }

}

$end = microtime(true);

$endMem = Memory_get_usage();

echo 'ByRef: ', $end - $start, 's' , PHP_EOL, 'Mem: ', $endMem - $startMem , PHP_EOL;

// END: 传值胜出

// 总结：数据需要修改的就用引用，数据不需要修改的就用非引用