Req #69626 [Fbk->Dup]: how check variable be defined ? how check variable be exists

Edit report at https://bugs.php.net/bug.php?id=69626&edit=1 ID: 69626 Updated by: daverandom@php.net Reported by: hark110 at 63 dot com Summary: how check variable be defined ? how check variable be exists -Status: Feedback +Status: Duplicate Type: Feature/Change Request Package: Variables related PHP Version: 5.6.8 Block user comment: N Private report: N Previous Comments: ------------------------------------------------------------------------ [2015-05-12 10:52:45] cmb@php.net Actually, this is a duplicate of bug #69476. Anyhow, I wonder why you have the need to distinguish undefined variables from variables with the value NULL. ------------------------------------------------------------------------ [2015-05-12 09:42:03] hark110 at 63 dot com Description: ------------ current php no best way check a variable whether be defined, only like below: if check $a whether be defined in global varibale: array_key_exists('a', $GLOBALS); in function or method: array_key_exists('a',get_defined_vars()) because isset, empty is not trust, see test script Test script: --------------- <?php function test() { //defined variable $a = null; var_dump(isset($a)); //false var_dump(is_null($a));//true var_dump(empty($a)); //true //undefined variable var_dump(isset($b));//false var_dump(empty($a)); //true var_dump(@is_null($c));//true, Notice: Undefined variable: a var_dump(get_defined_vars());//$b,$c undefined, $a is defined and value is NULL //be unset() variable $d; unset($d); var_dump(empty($a)); //true var_dump(isset($d));//false var_dump(@is_null($d));//true,Notice: Undefined variable: a var_dump(get_defined_vars());//$b,$c undefined,$d be unset and defined, $a is defined and value is NULL //empty string variable $e = ''; var_dump(empty($e)); //true var_dump(isset($e)); // true var_dump(is_null($e)); //false var_dump(get_defined_vars());//$b,$c undefined,$d be unset and undefined, $a is defined and value is NULL, $e is defined and value is empty string } test(); Expected result: ---------------- <?php $a; var_dump(isset($a)); // is false Actual result: -------------- <?php $a; var_dump(isset($a)); // is true ?> or <?php $a; var_dump(isdefined($a)); //is true ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=69626&edit=1