{"id":688,"date":"2012-01-21T16:12:51","date_gmt":"2012-01-22T00:12:51","guid":{"rendered":"http:\/\/virendrachandak.wordpress.com\/?p=688"},"modified":"2025-12-17T09:51:25","modified_gmt":"2025-12-17T17:51:25","slug":"php-isset-vs-empty-vs-is_null","status":"publish","type":"post","link":"https:\/\/www.virendrachandak.com\/techtalk\/php-isset-vs-empty-vs-is_null\/","title":{"rendered":"PHP isset() vs empty() vs is_null()"},"content":{"rendered":"

PHP has different functions which can be used to test the value of a variable. Three useful functions for this are isset()<\/strong>, empty()<\/strong> and is_null()<\/strong>. All these function return a boolean value. If these functions are not used in correct way they can cause unexpected results.<\/p>\n

isset() and empty() are often viewed as functions that are opposite, however this is not always true. In this post I will explain the differences between these functions.<\/p>\n

<\/p>\n

\n

isset()<\/h4>\n

From PHP manual – isset()<\/a>:<\/p>\n

isset \u2014 Determine if a variable is set and is not NULL<\/p>\n<\/blockquote>\n

In other words, it returns true<\/strong> only when the variable is not null<\/strong>.<\/p>\n<\/div>\n

\n

empty()<\/h4>\n

From PHP Manual – empty()<\/a>:<\/p>\n

empty \u2014 Determine whether a variable is empty<\/p>\n<\/blockquote>\n

In other words, it will return true<\/strong> if the variable is an empty string, false, array(), NULL, \u201c0?, 0, and an unset variable.<\/p>\n<\/div>\n

\n

is_null()<\/h4>\n

From PHP Manual – is_null()<\/a>:<\/p>\n

is_null \u2014 Finds whether a variable is NULL<\/p>\n<\/blockquote>\n

In other words, it returns true<\/strong> only when the variable is null<\/strong>. is_null() is opposite of isset(), except for one difference that isset() can be applied to unknown variables, but is_null() only to declared variables.<\/p>\n<\/div>\n

The table below is an easy reference for what these functions will return for different values. The blank spaces means the function returns bool(false)<\/strong>.<\/div>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Value of variable ($var)<\/th>\nisset($var)<\/th>\nempty($var)<\/th>\nis_null($var)<\/th>\n<\/tr>\n
“” (an empty string)<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
” ” (space)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
FALSE<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
TRUE<\/td>\nbool(true)<\/td>\n<\/td>\n<\/td>\n<\/tr>\n
array() (an empty array)<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
NULL<\/tt><\/td>\n<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/tr>\n
“0” (0 as a string)<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
0 (0 as an integer)<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
0.0 (0 as a float)<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/tr>\n
var $var;<\/em> (a variable declared, but without a value)<\/td>\n<\/td>\nbool(true)<\/td>\nbool(true)<\/td>\n<\/tr>\n
NULL<\/tt> byte (“\\ 0”)<\/td>\nbool(true)<\/td>\n<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

I have tested the above values in following PHP versions:<\/p>\n

\n
\n