How to use php isset

php isset function is used to detect whether a variable is set. Its syntax is "bool isset (mixed $var [, mixed $...] )". The parameter "var" represents the variable to be checked. If isset is used Testing a variable set to NULL will return FALSE.

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PHP isset() Function

Definition and usage

isset() — Check whether a variable is set.

Syntax

bool isset ( mixed $var [, mixed $... ] )

Check whether the variable is set and not NULL.

If a variable has been released using unset(), it will no longer be isset(). If you use isset() to test a variable that is set to NULL, it will return FALSE. Also note that a NULL byte ("\0") is not equivalent to PHP's NULL constant.

Parameters

var The variable to be checked.

Return value: TRUE if var exists and the value is not NULL, otherwise FALSE.

PHP version: PHP 4, PHP 5, PHP 7

Example

Run result:

This var is set so I will print.bool(true) bool(true) bool(false) bool(false) bool(false)

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