[SOLVED]=== what does it do?

Lee · #1 (**permalink**) 08-08-2007, 02:07 PM

As the title says what does === mean when you use it in php?

Theres = for assigning things and theres == for equal to, the best description i have so far is...

PHP Code:

  if(somebooleanfunction($var) === TRUE){

//Statements

}

That would work where as:

PHP Code:

  if(somebooleanfunction($var) == TRUE){

//Statements

}

Would not work, is that right?

Can anyone say where else === can be used and why it should be?

Thanks for any help.

TeraTask · #2 (**permalink**) 08-08-2007, 03:07 PM

While not easy to find, this will be helpful: PHP: PHP type comparison tables - Manual

Let me know if you have any other questions.

Lee · #3 (**permalink**) 08-08-2007, 03:15 PM

Quote:

Originally Posted by TeraTask

While not easy to find, this will be helpful: PHP: PHP type comparison tables - Manual

Let me know if you have any other questions.

That does help quite a bit, i am just trying to get my head round it all, when i come to use it soon i am now confident i will be able to use it.

Thanks.

rpgfan3233 · #4 (**permalink**) 08-08-2007, 03:26 PM

I recently used === in a PHP script of my own. One area where === is useful is true/false v.s. non-zero and non-false values. Any non-false and non-zero value is considered true. In other words, if you are testing for a boolean value to be returned from a function (i.e. a PHP function returns FALSE on error, but its return value is defined as int), you should use === instead of == .

In fact, there is a noticeable warning present in the documentation for the strpos function. For those that don't feel like loading a page (especially those who still use dial-up or have a similar slow connection), here is the warning:

Quote:

Warning

This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

PHP Code:

  $needle = 'hELLO';

$haystack = 'Hello World!';

$pos = strpos($haystack, $needle);

if ($pos === false)

    echo "$needle could not be found in $haystack.";

else

    echo "$needle was found at position $pos in $haystack.";

 
$needle = 'Hello';

$pos = strpos($haystack, $needle);

if ($pos === false)

    echo "$needle could not be found in $haystack.";

else

    echo "$needle was found at position $pos in $haystack.";

Lee · #5 (**permalink**) 08-08-2007, 03:54 PM

So are you saying that instead of:

PHP Code:

  if ($var == $var2){
//do things
}

//i should use...?

if ($var === $var2){
//do things
}

TeraTask · #6 (**permalink**) 08-08-2007, 04:06 PM

It just depends on the type of information that you're trying to compare and how you want to compare it.

PHP Code:

  //Let's say we have this function
//NOTE: All functions do what they say they'll do, even if not defined.
function number_of_members_attending($meeting_id) {
  if (meeting_exists($meeting_id)) {
    //Now, calculate the number of members and store in $number_of_members

    return $number_of_members;
  } else {
    //Meeting doesn't exist, so this question is inappropriate
    return false;
  }
}

Now, this function will return 3 possible values of interest:

1) false if the meeting_id is invalid or no meeting exists;
2) 0 if the meeting has no registered users;
3) > 0 if the meeting has some number of members.

Now, let's say that you were writing code which uses the function above:

PHP Code:

  $members_attending = number_of_members_attending(20070315);
if ($members_attending) {
  echo "There are ".$members_attending." members attending your meeting.";
} else {
  echo "No meeting is scheduled.";
}

The code above would be inaccurate as a meeting may be scheduled and no members set to attend yet, so you could be more explicit by using:

PHP Code:

  $members_attending = number_of_members_attending(20070315);
if ($members_attending === false) {
  echo "No meeting is scheduled.";
} elseif ($members_attending == false) {  //I'm just doing that as an example, normally I'd use $members_attending == 0
  echo "No one is scheduled to attend this meeting yet.";
} else {
  echo "There are ".$members_attending." members attending your meeting.";  
}

By using identically equal ( === ) I am able to specifically distinguish between false and 0 which matters in this case (and, also, in the strpos case).

I hope that helps!

Lee · #7 (**permalink**) 08-08-2007, 04:21 PM

Quote:

Originally Posted by TeraTask

I hope that helps!

That helped out great, i think i can now say i understand it fully as i ever will do, if i have any problems i will get back to you all.

Thanks

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The Following User Says Thank You to TeraTask For This Useful Post:
Lee (08-08-2007)

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Lee (08-08-2007)