== and === (Strange Error)

[jaswinder_rana]

PHP5/IIS/Windows 2003/Smarty

I have 2 conditions

$value = 1;
$selected = 2;
if(($value === $selected) )
{
    echo  'TRUE'; //DOESN'T work, which is correct
}
if(($value == $selected) )
{
    echo  'TRUE'; //WORKS, which is WRONG
} 

The 2nd condition should evaluate to false but it's evaluating to true.

I am not sure why, but it's driving me mad.

Please help

[logic_earth]

$a = 1;
$b = 2;
var_dump($a == $b); 

Outputs false hmmm

[Kieran.in]

PHP5/IIS/Windows 2003/Smarty

I have 2 conditions

$value = 1;
$selected = 2;
if(($value === $selected) )
{
    echo  'TRUE'; //DOESN'T work, which is correct
}
if(($value == $selected) )
{
    echo  'TRUE'; //WORKS, which is WRONG
} 

The 2nd condition should evaluate to false but it's evaluating to true.

I am not sure why, but it's driving me mad.

Please help

#
First theres no need for the double brackets.

$value = 1;
$selected = 2;

if ($value == $selected )
{
    echo  'Second one TRUE'; //WORKS, which is WRONG
}

if ($value === $selected )
{
    echo 'First one TRUE'; //DOESN'T work, which is correct
} 

Try that, not sure if it will make much of a difference, could be a tedious error, or might have been recognised as a ternary statement.

(p.s. if your testing its fine; but if you want to return a true/false boolean expression make sure you return it and don't echo it.)

[Kieran.in]

Just making sure, your not doing this inside a function and trying to get a boolean value back are you?

[jaswinder_rana]

Thanks.

I am just debugging (with echo statements) as the function wasn't returning correct values

Now I tried your code with SPECIFIC values MANUALLY entered (1 and 2) and it worked as expected.

But, when I use as it as before (with values via parameters) it doesn't work fine.

Following is the output


2 == 2_2
Second one TRUE

as you can see, both values (I just printed those inside the == IF statement, just to make sure) are NOT equal, yet it's still computing it as true.



BTW, the function I am trying is a Smarty Plugin (http://smarty.incutio.com/?page=select) inside my template.

[logic_earth]

2_2 gets converted to an integer so 2 == 2 == true

[jaswinder_rana]

But, Why would it gt converted to an integer?

There is no casting function and I am just comparing string.

[Kieran.in]

try...

$value =(int) 1;

$selected =(int) 2;



if ($value == $selected )

{

    echo  'Second one TRUE'; //WORKS, which is WRONG

}



if ($value === $selected )

{

    echo 'First one TRUE'; //DOESN'T work, which is correct

} 

[jaswinder_rana]

I tried that and even WITHOUT (int), it works fine.

Which means BOTH are FALSE.

[logic_earth]

when you test a string against an integer it is converted to an integer.
This is not the case with === as it also test type.

[jaswinder_rana]

Ah I see.

But, isn't PHP loose type? I guess it does all of it in background then? because for compiler their types are different?

[earl-grey]

Two values of different types can't be compared as-is. Either the first or the second one needs to be converted. When values are a string and an integer, string value is converted to integer.

[Cups]

This variable and array tests might shed some light for you.

PHP thinks 1 and "1thing" are the same value (n.b. that is to say, they are not identical but when interpreted their values are the same ...) ,well PHP has to start somewhere when comparing what could be ridiculous values ... so it seems to start with integers.

We get lots of benefits - but we really need to appreciate the rules being applied "behind the scenes" as it were.

The matrix above, if nothing else, should scream out three things:

1. Don't take anything for granted when using comparison operators 'till, well, 'till I guess till you've learned them
2. Use var_dump() when you are trying to figure out wtf is going wrong
3. Print off that page and nail it to the wall

Learn to love ===

[jaswinder_rana]

Thanks.

That page is ....interesting