PHP中isset与array_key_exists的区别实例分析

PHP中isset与array_key_exists的区别实例分析_PHP教程

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풀어 주다： 2016-07-13 09:52:13

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PHP中isset与array_key_exists的区别实例分析

　　本文实例讲述了PHP中isset与array_key_exists的区别。分享给大家供大家参考。具体分析如下：

　　1.对于数组值的判断不同，对于值为null或''或false,isset返回false，array_key_exists返回true;

　　2. 执行效率不同，isset是内建运算符，array_key_exists是php内置函数，isset要快一些。请参考：PHP 函数实现原理及性能分析

　　3.当用isset访问一个不存在索引数组值时，不会引起一个E_NOTICE的php错误消息;

　　4.array_key_exists 会调用get_defined_vars判断数组变量是否存在，isset不用;

　　测试代码：

function

microtime_float()

{

list($usec, $sec) = explode(" ", microtime());

return ((float)$usec + (float)$sec);

}

$test_arr['aa']='dd';

$test_arr['bb']='';

$test_arr['cc']=NULL;

$test_arr['dd']=false;

$test_arr= array('aa'=>'dd','bb'=>'','cc'=>null,'dd'=>false);

echo "isset aa is ";var_dump(isset($test_arr['aa']));echo "\n";

echo "isset bb is ";var_dump(isset($test_arr['bb']));echo "\n";

echo "isset cc is ";var_dump(isset($test_arr['cc']));echo "\n";

echo "isset dd is ";var_dump(isset($test_arr['cc']));echo "\n";

echo "isset none is ";var_dump(isset($test_arr['none']));echo "\n";

echo "key_exist aa is ";var_dump(array_key_exists('aa',$test_arr));echo "\n";

echo "key_exist bb is ";var_dump(array_key_exists('bb',$test_arr));echo "\n";

echo "key_exist cc is ";var_dump(array_key_exists('cc',$test_arr));echo "\n";

echo "key_exist dd is ";var_dump(array_key_exists('dd',$test_arr));echo "\n";

echo "key_exist none is ";var_dump(array_key_exists('none',$test_arr));echo "\n";

$time_start = microtime_float();

for($i=0;$i

isset($test_arr['aa']);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "isset 100 is $time\n";

for($i=0;$i

isset($test_arr['aa']);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "isset 10000 is $time\n";

for($i=0;$i

isset($test_arr['aa']);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "isset 1000000 is $time\n";

//++++++++++++++++++++++++++++++

$time_start = microtime_float();

for($i=0;$i

array_key_exists('aa',$test_arr);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "array_key_exists 100 is $time\n";

for($i=0;$i

array_key_exists('aa',$test_arr);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "array_key_exists 10000 is $time\n";

for($i=0;$i

array_key_exists('aa',$test_arr);

}

$time_end = microtime_float();

$time = $time_end - $time_start;

echo "array_key_exists 1000000 is $time\n";

　　希望本文所述对大家的php程序设计有所帮助。