Whats the difference between !== and !=

[jwhite68]

Until recently, I had understood that !== and != were the same.  However, while trying to solve a bug, I found that the problem was checking !== instead of !=.  Can anyone throw any light on this subject?

[GingerRobot]

The equality comparison (==) will return true if two variables are equal. The identical comparison (===) will return true if the variables are equal AND of the same type.

 

<?php
if(0=='0'){
//true
}

if (0 === '0'){
//false
}
?>

[NArc0t1c]

I guess PHP handles != as if was declaring a variable.

The ! in front is probably not used as it picks up the = and not two ==.

[Lumio]

Hi

!== and != is the converse of === and ==

So I give you an example:

You got two variables

One with the value true and one with the value 1:

Now the first request with !=

<?php
   $var1 = true;
   $var2 = 1;

   if ($var1 != true)
      echo 'The value of $var1 is false';
   else
      echo 'The value of $var1 is true';

   if ($var2 != true)
      echo 'The value of $var2 is false';
   else
      echo 'The value of $var2 is true';
?>

Now the same with !==

<?php
   $var1 = true;
   $var2 = 1;

   if ($var1 !== true)
      echo 'The value of $var1 is false';
   else
      echo 'The value of $var1 is true';

   if ($var2 !== true)
      echo 'The value of $var2 is false';
   else
      echo 'The value of $var2 is true';
?>

See the different?

 

So != controlls if the two values are the same but don't look after type of the two values.

!== controlls both... type of the variable and the values itself.

[jwhite68]

Hmm. I think I understand.

 

In my case, I was testing whether a variable (that could be assigned to a date field from a $_REQUEST['date']) was a null string or not.

 

So I am trying to understand whether its best practise to always use != for such scenarios.

Since !== doesnt work in this comparison.