learning ternery operator

[redarrow]

Advance thank you as i have been learning php for a while i fort i get a new php 5 bible book

to see what i need to brush up on there are 45 chapters and i am on chapter 6

 

i need your help cheers.

 

I am learning the tenery operator from the below example but the result is always true why?

 

Can you clear this opertor up so i understand it properly.

 

 

// ? means if

 

// : means is true

 

<?php

$a=10;

$b=20;

if($a === $b ? $a : $b ){

echo " correct a is larger then b";
}else{
echo " not correct a is not larger then b";
}
?>

[kenrbnsn]

The problem here is that you are using the triple equal sign, "===", which means the condition is true if the types of the arguments are the same.

 

The tenery operartor is a short way of doing an "if-else" block. The next two snippets of code do the same thing:

<?php
$a = 10;
$b = 20;
$result = ($a == $b)?$a:$b;
echo $result;
?>

 

<?php
$a = 10;
$b = 20;
if ($a == $b)
   $result = $a;
else
   $result = $b;
echo $result;
?>

 

Ken

[.josh]

well okay, that's sort of true, but not entirely relevant here.. the problem redarrow is that yes, a ternary operator is a condition. So the problem here is that you have a condition nested inside a condition.  A condition will evaluate true or false.  Look at your code:

 

<?php

$a=10;

$b=20;

if($a === $b ? $a : $b ){

echo " correct a is larger then b";
}else{
echo " not correct a is not larger then b";
}
?>

You assign a value to $a and $b first.  Next you have an 'if' condition.  'if' what?  inside your 'if' statement you do a ternary operation.  if $a === $b return $a if it's true, $b if it's false.  So either way, it will return a value, since you assigned a value to both variables.  Therefore, your original 'if' statement will always look like one of the two:

 

if($a) { ...}

 

or

 

if($b) { ... }

 

since you assigned something to both of them in the first place, it will always return true.

 

edit:

 

the point of the ternary operator is, as ken stated: a shorthand if..else statement. 

 

if(true) {
  $blah = something;
else {
  $blah = something else;
}

 

can be shortened to a ternary operator like this:

$blah = (true) ? something : something else;

 

example:

 

$x = 1;
$blah = ($x == 1) ? "one" : "not one";

 

[boo_lolly]

a sample of the way i do it:

(($a == $b) ? ("print something") : ("print something else"));

[kenrbnsn]

The OP edited his original example while I was typing my response which is why it doesn't relate. His original example was

<?php
$a=10;

$b=20;

$result = $a === $b ? $a : $b;

if ($result) {
echo " correct a is larger then b";
}else{
echo " not correct a is not larger then b";
}
?>

Which is not correct either.

 

Ken

[redarrow]

I done it this way ?

 

Thank you all for your support and examples cheers.

 

<?php
$a=100;
$b=200;
$c=900;
$d=1000;
$result=($a >$b)?$a:$b?$c:$b?$d:$a; 
echo $result;
?>

[redarrow]

i would like to no how this relates to programming the long way in speed or is all the ternary operator for programmers prefrence in style or is there a reel reason to use this style of programming?

[artacus]

I've never seen that before. I don't think it works.

I've tried it and it always evaluates to $d.

If it does work, its not at all clear what it is doing.

[artacus]

is there a reel reason to use this style of programming?

 

I use it often for little things like this:

 

$css = ($i++ % 2) ? 'class="odd"' : 'class="even"';

[boo_lolly]

i would like to no how this relates to programming the long way in speed or is all the ternary operator for programmers prefrence in style or is there a reel reason to use this style of programming?

 

i use it for small if statements. and to keep my code tidyer.

 

<?php
        $sql = "SELECT * FROM my_table";
        $query = mysql_query($sql);
        echo "<select name=\"drop_down\">\n";
        while($row = mysql_fetch_array($query)){
                echo "<option value=\"". $row['column1'] ."\"". (($row['column1'] == $_POST['drop_down']) ? (" SELECTED") : ("")) .">". $row['column2'] ."\n";
        }
        echo "</select>\n";

[kenrbnsn]

if you write that as

<?php
$a=100;
$b=200;
$c=900;
$d=1000;
$result=((($a >$b)?$a:$b)?$c:$b)?$d:$a; 
?>

Here is what is happening:

($a>$b) is evaluated first and is "false", so the expression's result is "$b" or "200".

200 is evaluated as "true", so the next part's result is "$c" or 900.

900 is also evaluated as "true", so the final answer is "$d" or 1000.

 

Ken

 

[redarrow]

Is this the correct way thank you all for your examples cheers.

<?php
$a=100;
$b=200;
$c=900;
$d=1000;
$result=(($a>$b)||($c>$d))? "true" : "not true" ? "true" : "not true" ; 
echo $result;
?>

[.josh]

redarrow, it mostly just boils down to preference.  That's why it's called shorthand.  Like the others, I use it for short things.  Mostly if I have a variable that's going to be assigned something based on either one thing or the other, and that's all that needs to be done for that condition, I simply use the ternary operator. 

 

I wouldn't recommend nesting ternary operators like that.  If for no other reason, because it can easily become confusing to you, the programmer.  You want to strive for elegant coding, but part of elegance is clarity and ease of reading (by humans).