What does if (! $ Variablename) do in PHP?

Question

I know that != "Not equal", but what does it mean when you have this:

 if(!$something) 

My first guess is related to exceptions, but the look of google returns nothing.

So what does that mean?

Answer 1

Regardless of what is in the variable, it is converted to a logical value (the variable itself, of course, remains intact), and then the NOT ( ! ) Operation is performed as a result of the Boolean. The conversion will happen because ! is a logical operator and works only with boolean values.

When converting to boolean, the following values ​​are considered FALSE:

• logical false itself
• integer 0 (zero)
• float 0.0 (zero)
• empty string and string "0"
• array with zero elements
• object with null member variables (PHP 4 only)
• special type NULL (including undefined variables)
• SimpleXML objects created from empty tags

Tip. If the variable does not have to be logical, you can use something more specific, for example isset($variable) , empty($variable) , $variable === '' , etc. depending on what you want to check. See the manual for more details.

Answer 2

This is the same as:

 if((bool)$something != true) { 

See: http://www.php.net/manual/en/control-structures.if.php

Answer 3

 if (!$something) { 

is an equivalent function

 if ($something == false) { 

Answer 4

Checks if something is fake.

Answer 5

It just means "If Not Something."

 if (!false) { this_happens_because_not_false_is_true(); } 

Answer 6

if(!$variable) same as if($variable == false) , so it checks if the $ false variable is false Look at @ bažmegakapa's answer to find out which values ​​are considered false.

Answer 7

Checks if $something false.

Answer 8

it checks if !$something false, or you can understand it as (if not $ something), then {// it will execute}, and if $ something is present, then it will not be entered in if

Answer 9

! $ variable - logical operator "Not" http://uk3.php.net/manual/en/language.operators.logical.php

it takes a logical meaning and flips it. True becomes false, and false becomes true.

Answer 10

It converts the variable to the boolean equivalent of the variable. This can be done in several cases:

 <?php // Case 1: $variable is boolean $variable = true; $variable = !$variable; // Changes to false; var_dump($variable); // bool(false) // Case 2a: $variable is a positive integer $variable = 5; $variable = !$variable; // Changes to false; var_dump($variable); // bool(false) // Case 2b: $variable is an integer other than 0 $variable = 0; $variable = !$variable; // Changes to false; var_dump($variable); // bool(true) // Case 2c: $variable is a negative integer $variable = -5; $variable = !$variable; // Changes to false; var_dump($variable); // bool(false) // Case 3a: $variable is string $variable = "Hello"; $variable = !$variable; // Changes to false; var_dump($variable); // bool(false) // Case 3b: $variable is empty string $variable = ""; $variable = !$variable; // Changes to false; var_dump($variable); // bool(true) ?> 

In short, this does the opposite of the empty() function! :)

Hope this helps! :)

Answer 11

 if($somethin == ""){ } Or if($somethin != ""){ }