Name a variable *before* it's populated?

[bookbuyer2000]

How can I make a script work where I want have stuff at the top at the script which use variables I name later? Here is an over-simplified example of what I mean:

<?php
$heading = 'Hello, welcome to the '.$subjectmatter.' forum. Thank you.
$subjectmatter = 'cake baking';
print $heading;
?>

Thanks!

p.s. I'll consider myself psychic if the first response to this post is "why don't you just name the variable first?" :p

[laserlight]

One approach would be to write a function:

<?php
function formatHeading($subjectmatter) {
    return 'Hello, welcome to the ' . $subjectmatter . ' forum. Thank you.';
}

print formatHeading('cake baking');

[bookbuyer2000]

Oh that's cool, I didn't think of that. (I should have thought of that because I was just recently giving myself a refresher course in functions).

I vaguely recall something I learned 5 or 6 years ago, something about variable variables, or using a variable word without the $ before it, then adding it later, or maybe it was using the ${$variable} thingy.... does that ring a bell? Would that be another way to solve my problem, other than using functions? If so, what's the correct code?

Thank you!!

[laserlight]

bookbuyer2000 wrote:

I vaguely recall something I learned 5 or 6 years ago, something about variable variables, or using a variable word without the $ before it, then adding it later, or maybe it was using the ${$variable} thingy.... does that ring a bell? Would that be another way to solve my problem, other than using functions? If so, what's the correct code?

That will not work because the variable is evaluated at the time the string is declared. What you could do is to use a placeholder that will not be evaluated, such as with [man]printf[/man]:

<?php
$heading = 'Hello, welcome to the &#37;s forum. Thank you.';
$subjectmatter = 'cake baking';
printf($heading, $subjectmatter);

[bookbuyer2000]

I never heard of placeholders? That's a new one for me. Now I'm curious -- what if you need just one placeholder, but 2 variables? How does PHP know which variable the "%s" refers to?

I ask because I have about a dozen variables I don't want to declare 'till later.

Here's an example:

<?php
$heading = 'Hello, welcome to the food forum for the month of %s. Thank you.';
$subjectmatter = 'cake baking';
$month = 'November';
$cake_flavor='Chocolate';

[johanafm]

The best thing to do is usually simply try doing whatever you want and see what happens. When you don't understand why something doesn't go wrong, go to the php doc for whatever function / language construct you are using, in this case [man]printf[/man], which in turn would tell you to see [man]sprintf[/man] as well.

printf() requires one function argument per placeholder (unless you are using numbered arguments). As such there can be no ambiguities.

printf($heading, $subjectmatter);
printf($heading, $month);
printf($heading, 'something else');

# but this will not work: number of arguments does not match the format of the $heading string.
printf($heading, '1', '2');