Analysis of differences between isset and array_key_exists in PHP

This article mainly introduces the differences between isset and array_key_exists in PHP, analyzes in detail the differences between isset and array_key_exists, and analyzes the specific usage of isset and array_key_exists, for more information about the differences between isset and array_key_exists in PHP, see the following example. Share it with you for your reference. The specific analysis is as follows:

1. the array values are different. if the values are null or ''or false, isset returns false, and array_key_exists returns true;

2. the execution efficiency is different. isset is a built-in operator, and array_key_exists is a php built-in function. isset is faster. See: PHP function implementation principles and performance analysis

3. when I use isset to access a non-indexed array value, it will not cause an E_NOTICE php error message;

4. array_key_exists will call get_defined_vars to determine whether the array variable exists, and isset does not need;

Test code:

<?phpfunction 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";

I hope this article will help you with php programming.