PHP isset () is used to determine whether a variable has set or not. In other words, the PHP isset() function checks whether a variable set with unset() function. If it isn’t NULL, it won’t be set. If the testing variable has a NULL value, it returns false.
Syntax of PHP is set()
bool Iset ( $var, mixed)
Parameters: This function can accept more than one parameter. $var is the first parameter. This parameter stores the variable’s value.
Note: This function returns true only if all variables have been set.
PHP Changelog: PHP5.4: Strings now return FALSE if they are not numeric offsets
Tip 1: You can unset a variable with the unset() function.
Tip 2: PHP will retrieve the field from your class as it is stored if you don’t have methods defined.
Tip 3: PHP Function can be overridden to create classes that are able to hold data as an array but can also be used like objects.
Example: PHP Program Use isset() function
$num = ‘0’;
{if( isset( $num ) ) If( isset ($num ))
Print_r(” $num) is used with the isset function
“;
|}
$array = array()
echo isset($array[‘deva’]) ?
“array is set.” : ‘array not set. ‘;
?>
Output:
With the isset function, 0 is set
array not set.