PHP isset() vs empty() vs is_null()

Credit: https://techtalk.virendrachandak.com/php-isset-vs-empty-vs-is_null/

 

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

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.

 

isset()

From PHP manual – isset():

isset — Determine if a variable is set and is not NULL

In other words, it returns true only when the variable is not null.

empty()
From PHP Manual – empty():

empty — Determine whether a variable is empty

In other words, it will return true if the variable is an empty string, false, array(), NULL, “0?, 0, and an unset variable.

is_null()
From PHP Manual – is_null():

is_null — Finds whether a variable is NULL

In other words, it returns true only when the variable is null. 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.

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).
Value of variable ($var) isset($var) empty($var) is_null($var)
“” (an empty string) bool(true) bool(true)
” ” (space) bool(true)
FALSE bool(true) bool(true)
TRUE bool(true)
array() (an empty array) bool(true) bool(true)
NULL bool(true) bool(true)
“0″ (0 as a string) bool(true) bool(true)
0 (0 as an integer) bool(true) bool(true)
0.0 (0 as a float) bool(true) bool(true)
var $var; (a variable declared, but without a value) bool(true) bool(true)
NULL byte (“\ 0″) bool(true)

 

Other News

What is Ajax

What is AJAX? AJAX = Asynchronous JavaScript and XML. In short; AJAX is about loading data in the background and display it on the webpage, without reloading the ...

Chi tiết

Absolute, Relative, Fixed Positioning: How Do They Differ?

Short answer: Yes, there is one more, "static", which is the default. Yes, they majorly differ. Each of them is incredibily useful and which you should ...

Chi tiết

CSS Font-Size: em vs. px vs. pt vs. percent

One of the most confusing aspects of CSS styling is the application of the font-size attribute for text scaling. In CSS, you’re given four different units by which you can ...

Chi tiết

How can I make Java print quotes, like “Hello”?

System.out.print("\"Hello\""); The double quote character has to be escaped with a backslash in a Java string literal. Other characters that need special treatment ...

Chi tiết

List diffirences between Java and C++

List diffirences between Java and C++ Java ...

Chi tiết

How to Create CSS3 Speech Bubbles Without Images

Credit: https://www.sitepoint.com/pure-css3-speech-bubbles/ I remember my creating my first ...

Chi tiết