User functions and parameter use

[Rubble]

I find I seem to write a few image modify programs and so I was going to create a function:

function resize( $width = 600, $height = 600, $background = 'White', $text = 'Watermark');
{
// Resize code
}

// Will give me a new image 600 wide 600 heigh on a white background watermarked with the text watermark.
resize( );

// Will give me a new image 800 wide 800 heigh on a gray background watermarked with the text Anthony.
resize( 800, 800, 'gray', 'Anthony'); 

If I want an image 600 wide 600 heigh on a gray background watermarked with the text watermark.
I can not do this as I will get an error:

resize( 'gray' ); 

So I will need to put values in for everything even though some of them are the same as the default values?

resize( 600, 600, 'gray', 'watermark'); 

It looks like it would be easier to define the variables and just use them in the function call and not have any defaults in the function?
Thinking about this if I wanted to create two different thumbnail sizes or similar I would need to set two lots of variables.

$width = 600;
$height = 600;
$background = 'gray';
$text = 'Watermark';

resize( $width, $height, $background, $text); 

What is a good way to go about this?

[Cups]

You could reorder the parameters based upon your experience of the likelihood that you are not going to override the defaults.

function resize( $background = 'White',  $text = 'Watermark', $width = 600, $height = 600); 
{ 
// Resize code 
} 

resize('gray'); 

OR,

hardcode the defaults in the function, and leave the param default as NULL (yuk)

function resize( $width = NULL, $height = NULL, $background = 'White', $text = 'Watermark'); 
{ 
if( $width===NULL ) $width = 800;
if( $height===NULL ) $height = 800;

// Resize code 
} 

resize(NULL, NULL, 'gray'); 

The benefits of these 2 is that your IDE may well prompt you to remind you of the order and help you fill them in as soon as it sees you write resize( ...

OR pass in an array of values and do say, a ternary check otherwise use a hardcoded default.

function resize( $params ); 
{ 
$background = (isset($params['background'])) ? $params['background'] : 'white';
$background = (isset($params['height'])) ? $params['height'] : 800;
$background = (isset($params['width'])) ? $params['width'] : 800;

// Resize code 
} 

$params = array('background' => "gray");
resize( $params ); 

This has the drawback that you have to remember the values names but not the order. It is however useful if your input is coming from a form, say, which is already in a post or get array - simply unset() the form elements you do NOT want to send to the resize - or the params array can be an sql result as an array.

<?php

// if this is spoofing your POST input ...
$_POST['background'] = 'green';
$_POST['height'] = '500';
$_POST['width'] = '500';
$_POST['submit'] = 'yes';

unset( $_POST['submit']);// ko this one

resize( $_POST );

This is one of those areas that OOP might excel if you wanted to load even more smarts into it.

$i = new Resizer($path_to_file);
$i->setWatermark('My text');
$i->setSize(300);
// where because only one size is defined, a square can be assumed. 

This carries much of the IDE benefits too.

[Rubble]

Thanks for the detailed reply; I did think about OOP but after our last discussion on the subject I was a bit unsure I could write the code

I think the most straight forward way of doing it is to leave out the defaults in the function and include them all in the function call. I thought there may be something I was missing in the function or function call method.