[Gllug] mySQL PHP

[Dave Cridland]

On 11 Jul 2001 12:41:47 +0000, Bruce Richardson wrote:
> 
> On 7/11/01, 11:25:10 AM, Dave Cridland <dave at cridland.net> wrote 
> regarding Re: [Gllug] mySQL PHP:
> 
> 
> > On 10 Jul 2001 19:38:15 +0100, Bruce Richardson wrote:
> > > On Tue, Jul 10, 2001 at 07:10:43PM +0100, Bruce Richardson wrote:
> > > >   $var1 = $var1 ? $var : "default value";
> > >
> > > Sorry:
> > >
> > >     $var1 = $var1 ? $var1 : "default value";
> > >
> > > --
> > > Bruce
> 
> > Although, in my quest for code that tells the programmer what's really
> > going on, I'd be more specific:
> 
> > if( !isset( $var ) ) {
> >       $var = $var_default;
> > }
> 
> No.  Your code does not do the same as mine.  Your code tests to see 
> if $var is set - my code tests whether $var has a TRUE value (i.e. any 
> value other than FALSE) and the test fails if $var1 either has a value 
> of FALSE or is unset.  A variable with a value of FALSE is set and 
> your code misses it.
> 
> 	If ($var) { $var = $var_default }
> 
> is correct.

Well, if you want to be pedantic, then:
 - $var is assumed to be coming from a form variable, or similar.
 - Your rewritten test does exactly the opposite of your original code.
 - If $var is 0, '', false, or unset, then you will overwrite with a
default value. '' and unset are both fine to test for, whereas a form
might reasonably treat an explicitly entered value of 0 as distinct from
a default value.

> Besides, not only is the ?: operator used in quite a few C-style 
> languages but it is explained in the introductory section of the PHP 
> manual.  Your quest is for code which will be understood by people who 
> haven't bothered to learn the language.

The trigraph is fine - I was just typing it out in full.

However, given that the lack of entry of a variable often means more
than simply using a default value, I'm inclined to use a full if
conditional, with the braces for stylistic reasons. (Otherwise, I've
seen other programmers simply add a line to the conditional without
adding the braces later.)

I'd imagine the usual handling of a form variable to look like:

global $HTTP_POST_VARS; // Because I'd assume we were in a function.
if( !isset( $HTTP_POST_VARS['var'] ) || !strlen( $HTTP_POST_VARS['var']
) ) {
	// Either:
	$var = SOME_SUITABLE_DEFAULT;
	// Or:
	my_add_error( 'Var was not specified in the form' );
}

For checking whether a form had been submitted, so as to know whether to
display a blank form, I'd do:

global $HTTP_POST_VARS;
if( isset( $HTTP_POST_VARS[ 'submit_button_name' ] ) ) {
	process_form();
} else {
	display_form();
}

I realise it's unlikely that the form submit button would have a value
which evaluated to false in a conditional, but neither does it hurt, and
it saves PHP from actually making the evaluation, making the code
marginally more efficient, IMHO.

Dave.

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