Hopefully a really easy question.

davidjay

I just book a book on PHP and MySQL and I'm going through the tutorials. I 'm tring to complete the activity at the end of the chapter and I can't get it to work. Prepare to be amazed at how much I don't know.

This is the code I'm entering:

<html>
<head>
<title>Listing 4.A2 Activity Exercise</title>
</head>
<body>
<?php
$five = 5;
$six = 6;
echo "$five > $six";
?>
</body>
</html>

This is the results:

5 > 6

This is the results I was hoping for:

False

What am I doing wrong. I've search the book and I can find an answer to such a basic question on any newsgroup.

HELP

TheDefender

You have to compare your comparison... (If that makes sense)

<?php 
$five = 5; 
$six = 6; 
If(($five > $six) == FALSE) echo "False";

// OR you could also do it this way...
If(!($five > $six)) echo "False";

?>

davidjay

But that's inputting the answer. When I open the script in internet explorer shouldn't it give me the answer w/o having to provide it myself.

TheDefender

I don't know af a way to output the result of a comparison the way you are trying to do it...

The comparison operator ( > ) symbol is used to make a comparison and is usually contained in an IF function, like I have shown you... The premise is to make the comparison and then do something based on that comparison.

In other words...

IF(5>6) {
// Do this if the comparison being made is FALSE
echo "False";
} else {
// Do this if it is TRUE
echo "True";
}

IF((5>6) == TRUE) {
// Do this if the comparison being made is TRUE
echo "True";
} else {
// Do this if it is FALSE
echo "False";
}

BuzzLY

Want to see something strange? Try loading this up in your browser:

echo true,false,true,false,true;

You would think that it would alternate between them, right? Wrong. It will output TRUE as "1", and FALSE as "".

PHP is not designed to send TRUE and FALSE values directly to the screen. It is designed to be used to help you branch your code.

Another thing to know about TRUE and FALSE. If you compare FALSE to 0 using ==, it will evaluate to TRUE. To compare the result to the actual value of FALSE, use ===, like so:

If ($check === FALSE) {

kmunk

As mentioned in previous post you can not print the value of FALSE - but you should be able to print a TRUE value meaning 1.

The reason you get 5>6 echo'ed on the screen is your quotation marks. Removing those will give you an empty screen since the evaluation is FALSE - making it

echo $five < $six;

will print 1 - as TRUE

bubblenut

been said before above but here's another way of doing it

echo $five > $six : 'true' : 'false';

kmunk

Just a little error in your inline if-statement

it should be:

echo $five > $six ? 'true' : 'false';

not

echo $five > $six : 'true' : 'false';

To davidjay I'd just wanna say that though you can print the true value it only makes sense to use comparisons to control further calculations as mentioned earlier.

e.g.
$zero = 0;
$five = 5;

if($zero == 0)

echo "Divide by zero";
else
echo $five/$zero;

Besides in your example you don't know whether the comparison is true or false - but you don't know that either in the if-statements. What you know is that it will either be true or false and therefore you can test that in the if statements and act on the result. E.g. printing TRUE or FALSE

davidjay

Thanks for all the replies. I couldn't figure out why the screen would come up blank. I though the browser would print false. Thanks again.

BuzzLY

Originally posted by kmunk
To davidjay I'd just wanna say that though you can print the true value it only makes sense to use comparisons to control further calculations as mentioned earlier.

e.g.
$zero = 0;
$five = 5;

if($zero == 0)

echo "Divide by zero";
else
echo $five/$zero;

A small caveat to this -- Try doing this:

$zero = "zero";
$five = 5;

if($zero == 0)  

    echo "Divide by zero";
else 
    echo $five/$zero;

Believe it or not, the if statment will evaluate as true. Granted, your code will probably never set $zero to a string, but what if you were getting it from a POST or GET? To prevent this, use ===. Of course, in this example, you would also need to make sure $zero was in fact a number, not a string.