作者：kuae_617 | 来源：互联网 | 2023-10-12 03:58
后端开发|php教程PHP,isset,array_key_exists,区别后端开发-php教程源码所有权著作权,ubuntu时区选哪里,安装版tomcat7,铁丝做爬虫,php
后端开发|php教程
PHP,isset,array_key_exists,区别
后端开发-php教程
源码所有权 著作权,ubuntu时区选哪里,安装版tomcat 7,铁丝做爬虫,php生成pdf文件变小,shoipfy seolzw
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；
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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
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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：
'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;$i<100;$i++){isset($test_arr[&＃039;aa&＃039;]);}$time_end = microtime_float();$time = $time_end - $time_start;echo "isset 100 is $time\n";for($i=0;$i<10000;$i++){isset($test_arr[&＃039;aa&＃039;]);}$time_end = microtime_float();$time = $time_end - $time_start;echo "isset 10000 is $time\n";for($i=0;$i<1000000;$i++){isset($test_arr[&＃039;aa&＃039;]);}$time_end = microtime_float();$time = $time_end - $time_start;echo "isset 1000000 is $time\n";//++++++++++++++++++++++++++++++$time_start = microtime_float();for($i=0;$i<100;$i++){array_key_exists(&＃039;aa&＃039;,$test_arr);}$time_end = microtime_float();$time = $time_end - $time_start;echo "array_key_exists 100 is $time\n";for($i=0;$i<10000;$i++){array_key_exists(&＃039;aa&＃039;,$test_arr);}$time_end = microtime_float();$time = $time_end - $time_start;echo "array_key_exists 10000 is $time\n";for($i=0;$i<1000000;$i++){array_key_exists(&＃039;aa&＃039;,$test_arr);}$time_end = microtime_float();$time = $time_end - $time_start;echo "array_key_exists 1000000 is $time\n";
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