PHP中isset与array_key_exists的区别实例分析

本文实例讲述了PHPissetarray_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 $timen";  for($i=0;$i<10000;$i++){  isset($test_arr['aa']);  }  $time_end = microtime_float();  $time = $time_end - $time_start;  echo "isset 10000 is $timen";  for($i=0;$i<1000000;$i++){  isset($test_arr['aa']);  }  $time_end = microtime_float();  $time = $time_end - $time_start;  echo "isset 1000000 is $timen";  //++++++++++++++++++++++++++++++  $time_start = microtime_float();  for($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 $timen";  for($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 $timen";  for($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 $timen";    

希望本文所述对大家的php程序设计有所帮助。

PHP中isset与array_key_exists的区别实例分析

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