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php not equal and || logical operator

OK, maybe it's late, but this is just driving me bananas.  I'm doing a simple logical operation which took in another program I wrote, but now it's just not seeming to work.  I've simplified my code dramatically to illustrate my issue:

<?php

$foobar = "null";
if (($foobar != "") || ($foobar != "null")) {
    echo "Not Equal";
} else {
    echo "Equal";
}

?>
The above code does not work... It always returns "Not Equal" no matter what $foobar is set to.


Now to drive me even more bananas, I've changed the != to == and it works fine!

$foobar = "null";
if (($foobar == "") || ($foobar == "null")) {
    echo "Equal";
} else {
    echo "Not Equal";
}

Does the PHP != operator have some special thing to get it to work right?  Why am I going nuts over this?  I just know I'm going to pound myself once someone offers the answer...

Thanks...
0
con2007
Asked:
con2007
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2 Solutions
 
nizsmoDeveloperCommented:
Does this illustrate your problem?

<?php
 
$foobar = null;
if ($foobar != "" || $foobar != null) {
    echo "Not Equal";
} else {
    echo "Equal";
}
 
?>

Open in new window

0
 
nizsmoDeveloperCommented:
basically you are assigning "null" as a string, not the actual null value which takes the meaning of empty.
hope this helps.
0
 
con2007Author Commented:
actually, I needed the null to be the actual value, not a null (bad example on my part).  You can change it to be this and it will still give the same problem:

$foobar = "jojo";
if (($foobar != "") || ($foobar != "jojo")) {
    echo "Not Equal";
} else {
    echo "Equal";
}
0
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nizsmoDeveloperCommented:
This example works fine or does it? please test:
<?php
$foobar = "jojo";
if ($foobar!="jojo" || $foobar=="") 
{
    echo "Not Equal";
} 
else 
{
    echo "Equal";
}
?>

Open in new window

0
 
nizsmoDeveloperCommented:
I see the problem with your original example, since it is a ||, only 1 condition has to satisfy!

Your example here:
$foobar = "jojo";
if (($foobar != "") || ($foobar != "jojo")) {
    echo "Not Equal";
} else {
    echo "Equal";
}

first condition $foobar!="" satisfies, so it will always echo "not equal".

Hope this helps.
0
 
b0lsc0ttIT ManagerCommented:
It is late. :)

The results seem correct to me.  The first script is setting $foobar to a string with the word null.  The If is using OR so it just gets to the first part.  The variable isn't empty (i.e. "") so the If is true and you get Not Equal.

The fix is to use and (i.e. &&).  If you want to have both be true then && is needed.

Let me know if you have a question or need more info.

bol
0
 
elfe69Commented:
Your example will always return "Not Equal" because at least one clause of your OR comparison will always be true:

if $foobar is "jojo", ($foobar != "") is true
if $foobar is "", ($foobar != "jojo") is true
if $foobar is "anything", ($foobar != "") and ($foobar != "jojo") are true
0
 
b0lsc0ttIT ManagerCommented:
To answer the second part of your question the fact that you test for Not Equal (i.e. !=) does make a difference, especially when the test uses OR.  In the case of Equal then Or works better (equals this OR that).  However when you use Not Equal then you have to be more cautious about the test.  You can't just switch the two (equal/not and &&/||) and expect the results to just be "opposite."

Let me know if you have a question.

bol
0
 
con2007Author Commented:
DOH! I knew it was going to be something ridiculous on my part!  Yes, it needs && not ||.

Thanks all!!
0
 
b0lsc0ttIT ManagerCommented:
Your welcome!  I'm glad I could help.  Thanks for the grade, the points and the fun question.

bol
0
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