这篇文章主要介绍了PHP中isset与array_key_exists的区别,较为详细的分析了isset与array_key_exists使用中的区别,并实例分析其具体用法,需要的朋友可以参考下
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:
- <?php
- 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;$i<100;$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;$i<100;$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。
新闻热点
疑难解答