Differences between isset and array_key_exists in PHP

Analyze the differences between isset and array_key_exists in PHP. Differences between isset and array_key_exists in PHP. Share it with you for your reference. The specific analysis is as follows: 1. analyze the differences between isset and array_key_exists in the array PHP

This article describes the differences between isset and array_key_exists in PHP. 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:

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Function Microtime_float () { List ($ usec, $ sec) = explode ("", microtime ()); Return (float) $ usec + (float) $ sec ); } $ Test_arr ['A'] = 'DD '; $ Test_arr ['BB '] = ''; $ Test_arr ['CC'] = NULL; $ Test_arr ['DD'] = false; $ Test_arr = array ('a' => 'DD', 'BB '=> '', 'CC' => null, 'DD' => false ); Echo "isset aa is"; var_dump (isset ($ test_arr ['A']); 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 ('A', $ 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 I <100; $ I ++ ){ Isset ($ test_arr ['A']); } $ Time_end = microtime_float (); $ Time = $ time_end-$ time_start; Echo "isset 100 is $ time \ n "; For ($ I = 0; I I <10000; $ I ++ ){ Isset ($ test_arr ['A']); } $ Time_end = microtime_float (); $ Time = $ time_end-$ time_start; Echo "isset 10000 is $ time \ n "; For ($ I = 0; I I <1000000; $ I ++ ){ Isset ($ test_arr ['A']); } $ Time_end = microtime_float (); $ Time = $ time_end-$ time_start; Echo "isset 1000000 is $ time \ n "; // ++ $ Time_start = microtime_float (); For ($ I = 0; I I <100; $ I ++ ){ Array_key_exists ('A', $ test_arr ); } $ Time_end = microtime_float (); $ Time = $ time_end-$ time_start; Echo "array_key_exists 100 is $ time \ n "; For ($ I = 0; I I <10000; $ I ++ ){ Array_key_exists ('A', $ test_arr ); } $ Time_end = microtime_float (); $ Time = $ time_end-$ time_start; Echo "array_key_exists 10000 is $ time \ n "; For ($ I = 0; I I <1000000; $ I ++ ){ Array_key_exists ('A', $ 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.

Examples in this article describes the differences between isset and array_key_exists in PHP. Share it with you for your reference. The specific analysis is as follows: 1. for arrays...