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：

1. <?php
2. function
3. microtime_float()
4. {
5. list($usec, $sec) = explode(" ", microtime());
6. return ((float)$usec + (float)$sec);
7. }
8. $test_arr['aa']='dd';
9. $test_arr['bb']='';
10. $test_arr['cc']=NULL;
11. $test_arr['dd']=false;
12. $test_arr= array('aa'=>'dd','bb'=>'','cc'=>null,'dd'=>false);
13. echo "isset aa is ";var_dump(isset($test_arr['aa']));echo "\n";
14. echo "isset bb is ";var_dump(isset($test_arr['bb']));echo "\n";
15. echo "isset cc is ";var_dump(isset($test_arr['cc']));echo "\n";
16. echo "isset dd is ";var_dump(isset($test_arr['cc']));echo "\n";
17. echo "isset none is ";var_dump(isset($test_arr['none']));echo "\n";
18. echo "key_exist aa is ";var_dump(array_key_exists('aa',$test_arr));echo "\n";
19. echo "key_exist bb is ";var_dump(array_key_exists('bb',$test_arr));echo "\n";
20. echo "key_exist cc is ";var_dump(array_key_exists('cc',$test_arr));echo "\n";
21. echo "key_exist dd is ";var_dump(array_key_exists('dd',$test_arr));echo "\n";
22. echo "key_exist none is ";var_dump(array_key_exists('none',$test_arr));echo "\n";
23. $time_start = microtime_float();
24. for($i=0;$i<100;$i++){
25. isset($test_arr['aa']);
26. }
27. $time_end = microtime_float();
28. $time = $time_end - $time_start;
29. echo "isset 100 is $time\n";
30. for($i=0;$i<10000;$i++){
31. isset($test_arr['aa']);
32. }
33. $time_end = microtime_float();
34. $time = $time_end - $time_start;
35. echo "isset 10000 is $time\n";
36. for($i=0;$i<1000000;$i++){
37. isset($test_arr['aa']);
38. }
39. $time_end = microtime_float();
40. $time = $time_end - $time_start;
41. echo "isset 1000000 is $time\n";
42. //++++++++++++++++++++++++++++++
43. $time_start = microtime_float();
44. for($i=0;$i<100;$i++){
45. array_key_exists('aa',$test_arr);
46. }
47. $time_end = microtime_float();
48. $time = $time_end - $time_start;
49. echo "array_key_exists 100 is $time\n";
50. for($i=0;$i<10000;$i++){
51. array_key_exists('aa',$test_arr);
52. }
53. $time_end = microtime_float();
54. $time = $time_end - $time_start;
55. echo "array_key_exists 10000 is $time\n";
56. for($i=0;$i<1000000;$i++){
57. array_key_exists('aa',$test_arr);
58. }
59. $time_end = microtime_float();
60. $time = $time_end - $time_start;
61. echo "array_key_exists 1000000 is $time\n";