在
PHP中优化功能的同时,我改变了
if(is_array($obj)) foreach($obj as $key=>$value { [snip] }
else if(is_object($obj)) foreach($obj as $key=>$value { [snip] }
至
if($obj == (array) $obj) foreach($obj as $key=>$value { [snip] }
else if($obj == (obj) $obj) foreach($obj as $key=>$value { [snip] }
在了解了===之后,我改变了
if($obj === (array) $obj) foreach($obj as $key=>$value { [snip] }
else if($obj === (obj) $obj) foreach($obj as $key=>$value { [snip] }
将每个测试从is_ *更改为投影导致重大加速(> 30％).
我明白===比==快,因为没有强制必须完成,但是为什么要调用变量比调用任何一个_ *函数要快得多？
编辑：
由于每个人都询问正确性,我写了这个小测试：
$foo=(object) array('bar'=>'foo');
$bar=array('bar'=>'foo');
if($foo===(array) $foo) echo '$foo is an array?';
if($bar===(object) $bar) echo '$bar is an object?';
它不会打印任何错误,并且两个变量都不会改变,所以我认为它是正常工作,但是我已经准备好相信它.
另一个编辑：
Artefacto的程序给了我以下数字：
PHP 5.3.2-1ubuntu4.2 (64bit) on a Core i5-750 with Xdebug Elapsed (1): 0.46174287796021 / 0.28902506828308 Elapsed (2): 0.52625703811646 / 0.3072669506073 Elapsed (3): 0.57169318199158 / 0.12708187103271 Elapsed (4): 0.51496887207031 / 0.30524897575378 Speculation: Casting and comparing can be about 1.7-4 times faster.
PHP 5.3.2-1ubuntu4.2 (64bit) on a Core i5-750 without Xdebug Elapsed (1): 0.15818405151367 / 0.214271068573 Elapsed (2): 0.1531388759613 / 0.25853085517883 Elapsed (3): 0.16164898872375 / 0.074632883071899 Elapsed (4): 0.14408397674561 / 0.25812387466431 Without Xdebug,the extra function call didn't matter anymore,so every test (except 3) ran faster.
PHP 5.3.2-1ubuntu4.2 on a Pentium M 1.6GHz Elapsed (1): 0.97393798828125 / 0.9062979221344 Elapsed (2): 0.39448714256287 / 0.86932587623596 Elapsed (3): 0.44513893127441 / 0.23662400245667 Elapsed (4): 0.38685202598572 / 0.82854390144348 Speculation: Casting an array is slower,casting an object can be faster,but might not be slower.
PHP 5.2.6-1+lenny8 on a Xeon 5110 Elapsed (1): 0.273758888245 / 0.530702114105 Elapsed (2): 0.276469945908 / 0.605964899063 Elapsed (3): 0.332523107529 / 0.137730836868 Elapsed (4): 0.267735004425 / 0.556323766708 Speculation: These results are similar to Artefacto's results,I think it's PHP 5.2.
解决方案：
我使用的分析器(Xdebug)使函数调用速度慢了3倍(即使没有分析),但并没有影响到转换和比较显着,所以铸造和比较看起来更快,即使它不受调试器/分析器.
我不能真正重现.事实上,除了一种情况,你的策略给了我更多的时间：
<?PHP
class A {
private $a = 4;
private $b = 4;
private $f = 7;
}
$arr = array("a" => 4,"b" => 4,"f" => 7);
$obj = new A();
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
is_array($obj) and die("err");
}
echo "Elapsed (1.1): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
($obj === (array) $obj) and die("err");
}
echo "Elapsed (1.2): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
is_object($arr) and die("err");
}
echo "Elapsed (2.1): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
($arr === (object) $arr) and die("err");
}
echo "Elapsed (2.2): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
is_object($obj) or die("err");
}
echo "Elapsed (3.1): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
($obj === (object) $obj) or die("err");
}
echo "Elapsed (3.2): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
is_array($arr) or die("err");
}
echo "Elapsed (4.1): " . (microtime(true) - $t);
echo "\n";
$t = microtime(true);
for ($i = 0; $i < 500000; $i++) {
($arr === (array) $arr) or die("err");
}
echo "Elapsed (4.2): " . (microtime(true) - $t);
输出：
Elapsed (1.1): 0.366055965424 Elapsed (1.2): 0.550662994385 Elapsed (2.1): 0.337422132492 Elapsed (2.2): 0.579686880112 Elapsed (3.1): 0.402997970581 Elapsed (3.2): 0.190818071365 Elapsed (4.1): 0.332742214203 Elapsed (4.2): 0.549873113632
演员和比较只是检查某物是否是一个对象的速度更快.推测如下：或许因为对象身份检查只需要确定处理程序表和对象句柄是否相同,而在最坏的情况下检查数组标识需要比较所有值.