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PHP中isset与array_key_exists的区别实例分析

2020-03-22 17:38:36
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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 $i++){isset($test_arr['aa']);$time_end = microtime_float();$time = $time_end - $time_start;echo "isset 100 is $time/n";for($i=0;$i 10000;$i++){isset($test_arr['aa']);$time_end = microtime_float();$time = $time_end - $time_start;echo "isset 10000 is $time/n";for($i=0;$i 1000000;$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 $i++){array_key_exists('aa',$test_arr);$time_end = microtime_float();$time = $time_end - $time_start;echo "array_key_exists 100 is $time/n";for($i=0;$i 10000;$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;$i 1000000;$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。PHP教程

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