Example analysis of the difference between isset and array_key_exists in PHP, _PHP tutorial

Example analysis of the difference between isset and array_key_exists in PHP,

This article gives an example of the difference between isset and array_key_exists in PHP. Share it with everyone for your reference. The specific analysis is as follows:

1. The judgment of array values ​​is different. If the value is 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, array_key_exists is a built-in function of PHP, and isset is faster. Please refer to: PHP function implementation principle and performance analysis

3. When using isset to access a non-existent index array value, an E_NOTICE php error message will not be caused;

4.array_key_exists will call get_defined_vars to determine whether the array variable exists, isset is not used;

Test code:

<&#63;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";

I hope this article will be helpful to everyone’s PHP programming design.

http://www.bkjia.com/PHPjc/1011250.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/1011250.htmlTechArticleExample analysis of the difference between isset and array_key_exists in PHP. This article explains the difference between isset and array_key_exists in PHP. Share it with everyone for your reference. The specific analysis is as follows: 1. For numbers...