php is null when empty?
PhpNullPhp Problem Overview
I have a question regarding NULL in PHP:
$a = '';
if($a == NULL) {
echo 'is null';
}
Why do I see is null when $a is an empty string? Is that a bug?
Php Solutions
Solution 1 - Php
What you're looking for is:
if($variable === NULL) {...}
Note the ===.
When use ==, as you did, PHP treats NULL, false, 0, the empty string, and empty arrays as equal.
Solution 2 - Php
As is shown in the following table, empty($foo) is equivalent to $foo==null and is_null($foo) has the same function of $foo===null. The table also shows some tricky values regarding the null comparison. (ϕ denotes an uninitialized variables. )
empty is_null
==null ===null isset array_key_exists
ϕ | T | T | F | F
null | T | T | F | T
"" | T | F | T | T
[] | T | F | T | T
0 | T | F | T | T
false | T | F | T | T
true | F | F | T | T
1 | F | F | T | T
\0 | F | F | T | T
Solution 3 - Php
check == vs ===
'' == NULL would return true
0 == NULL would return true
false == null would return true
where as
'' === NULL would return false
0 === NULL would return false
false === NULL would return false
Solution 4 - Php
No it's not a bug. Have a look at the Loose comparisons with == table (second table), which shows the result of comparing each value in the first column with the values in the other columns:
TRUE FALSE 1 0 -1 "1" "0" "-1" NULL array() "php" ""
[...]
"" FALSE TRUE FALSE TRUE FALSE FALSE FALSE FALSE TRUE FALSE FALSE TRUE
There you can see that an empty string "" compared with false, 0, NULL or "" will yield true.
You might want to use is_null [docs] instead, or strict comparison (third table).
Solution 5 - Php
This is not a bug but PHP normal behavior. It happens because the == operator in PHP doesn't check for type.
'' == null == 0 == false
If you want also to check if the values have the same type, use === instead. To study in deep this difference, please read the official documentation.
Solution 6 - Php
If you use ==, php treats an empty string or array as null. To make the distinction between null and empty, either use === or is_null. So:
if($a === NULL) or if(is_null($a))
Solution 7 - Php
PHP 7 isset() vs empty() vs is_null()
Solution 8 - Php
Just to addon if someone is dealing with , this would work if dealing with .
Replace it with str_replace() first and check it with empty()
empty(str_replace(" " ,"" , $YOUR_DATA)) ? $YOUR_DATA = '--' : $YOUR_DATA;
Solution 9 - Php
NULL stands for a variable without value. To check if a variable is NULL you can either use is_null($var) or the comparison (===) with NULL. Both ways, however, generate a warning if the variable is not defined. Similar to isset($var) and empty($var), which can be used as functions.
var_dump(is_null($var)); // true
var_dump($var === null); // true
var_dump(empty($var)); // true
Read more in How to check if a variable is NULL in PHP?
Solution 10 - Php
Use empty - http://php.net/manual/en/function.empty.php.
Example:
$a = '';
if(empty($a)) {
echo 'is empty';
}