! is so f' useless!!!

feldon23

Why did they put ! as a possible evaluation/conditional if it is totally f' useless?

if (!$user) {
do something;
}

if (!isset($user)) {
do something;
}

These are analagous SOMETIMES but not ALL the time.

Took me 2 hours+ of screwing around and yelling at the computer to figure out that trusting any evaluation to ! alone is a good way to waste an afternoon.

Hopefully this serves as a warning to others.

I put this in the same category as the totally useless urlencode() and urldecode(). When dealing with spaces and periods in passing variables through URLs, use rawurlencode() and rawurldecode(). And even in this case, I ended up writing a function to convert spaces to %20 (And then had the nightmare of urlencode trying to change all my % symbols to %25)!!!

And don't get me started on the statement in the PHP manual that you don't need to use urlencode and urldecode in most cases because "the browser does it for you".

With the value maybe, but not with the variable name!

<form action="{$php_self}" method="POST">
<input name="DSCF4023.jpg" type="text" length="40">
<input name="Cool Photo.jpg" type="text" length="40">
<input name="submit" type="submit" value="Go!">
</form>

What you get back is total frickin gobbledygook!

Here's what $_POST comes out like:

$_POST = array(
'DSCF4023_jpg' => 'whatever',
'Cool%20Photo_jpg' => 'whatever');

God that killed me for an hour+ cause IE turns the %20 back into a space before you can see it so the problem was hidden.

Don't you love how IE interprets EVERYTHING as HTML even if no HTML headers have been sent? I guess you have to use <nohtml> 🙁

Sorry, just had to vent.

Mordecai

Umm, ! works perfectly. It means "not."
If it's not working for you, perhaps you should read a tutorial about operators, and then rewrite your code.

feldon23

Tell me why when $user is empty, the code inside this IF statement executes:

if (!$user) {
echo "$user has a value!";
}

Cause that's what it was doing today until I changed it to !isset($user)

Mordecai

Set and empty are two different things entirely. Because something is empty doesn't mean it's not set.

stolzyboy

well i can't tell you why !$user didn't work and !isset($user) worked, but don't blame it on the poor !, since you are still using it in the isset part, could be something else with your code further up

BeastRider

Originally posted by feldon23
Tell me why when $user is empty, the code inside this IF statement executes:

if (!$user) {
echo "$user has a value!";
}

Cause that's what it was doing today until I changed it to !isset($user)

Don't know what you mean by "$user is empty" but unless you specfically declare a variable as boolean, you must be careful as to what assumptions you make about what cause the expression to evaluate to false.

Do you mean that $user is null? From

http://www.php.net/manual/en/language.types.boolean.php

If you aren't sure whether your variable is actually a boolean or not, be very careful with it. For whatever reason, a true boolean is stored as the number 1, and a false boolean is stored as nothing, null, empty string, or whatnot. Thus,

$myBool = true ; print( $myBool ) ;

is indistinguishable from

print( "" ) ;

likewise,

&myBool = false ; print( $myBool ) ;

is indistinguishable from

print( 1 ) ;

In addition to the above warnings about boolean evaluation, note that testing for equality is particularly unintuitive. In particular, "false" the string will equate to true. For example,

$myTrueBool = true ;
if( $myTrueBool == "true" ) print("it's true!") ;
if( $myTrueBool == "false" ) print("it's false!") ;
if( $myTrueBool == "mushroom" ) print("it's a mushroom!") ;
if( $myTrueBool == 4 ) print("it's the number 4!") ;

will print out

it's true!
it's false!
it's a mushroom!
it's the number 4!

But if $myTrueBool were false, instead, you'd get nothing at all. Caveat Usor.

matt_4013

Just as a side note to the above post, if you change:

$myTrueBool = true ;
if( $myTrueBool == "true" ) print("it's true!") ;
if( $myTrueBool == "false" ) print("it's false!") ;
if( $myTrueBool == "mushroom" ) print("it's a mushroom!") ;
if( $myTrueBool == 4 ) print("it's the number 4!") ;

to:

$myTrueBool = true ;
if( $myTrueBool === "true" ) print("it's true!") ;
if( $myTrueBool === "false" ) print("it's false!") ;
if( $myTrueBool === "mushroom" ) print("it's a mushroom!") ;
if( $myTrueBool === 4 ) print("it's the number 4!") ;

You will get no output. But if you change the condition of the first if statement to true instead of "true", you will get "it's true!" printed.

When doing things like

if(!$result = mysql_query($sql)) { 
echo "Error!";
}

although it will NORMALLY work, in some cases you'll get an incorrect condition. What you should really be doing is this

if(($result = mysql_query($sql)) === false) {
echo "Error!";
}

So that the entire statement equates to false, and not just an empty result set of 0.

laserlight

No offense intended, but your rant doesnt really mean much more except that you (like the rest of us) still have things to learn.

"These are analagous SOMETIMES but not ALL the time."
They arent the same at all.
Neither is a variable being empty the same as a variable being not set, as Mordecai noted.

Just because some feature isnt working as you expect doesnt make it totally useless.
I once noted that functions like fputs() are totally useless, since (for the case of fputs()) it is an alias for fwrite()
Is that entirely true? Maybe, maybe not.