how do professional PHP developers handle defaults for function parameters?

[lawrence k]

I'm working in PHP 4. Even if a parameter is mandatory, I nearly
always give it a default value of "false". Then I print an error
message if someone who is calling my function forgot the mandatory
parameter:

function outputHtmlToShowFile($fileName=false) {
if ($fileName) {
// code goes here
} else {
echo "In outputHtmlToShowAFile() the code expected the first
parameter to be a file name, but instead the value was false";
}
}

How do others handle default parameter values?

I've been avoiding this:

function outputHtmlToShowFile($fileName) { }

because if I do this and someone forgets to pass a file name to the
function, then the PHP parser issues an error. I've been assuming
that relying on the PHP parser to write my error messages for me is
unprofessional. Does anyone else feel that way?

[Henk verhoeven]

lawrence k wrote:

How do others handle default parameter values?

I guess you mean "how do others handle missing parameters?"

Well, on the development server my error handler will produce a walkback
so that i can see where the call was coming from.

Example:

/** class of the user interface component being called upon
class PntFilterFormPart extends PntPagePart {

*// function that will be called */
function setImplicitCombiFilter(&$combiFilter) {

(....)

/** Front controller class /*
class Site extends PntSite {

function setErrorHandler() {
includeClass('ErrorHandler');
$this->errorHandler =& new ErrorHandler();
$this->errorHandler->startHandling();
}

(....)

/* class of the actual controller producing the requested page, contais
the errorneous call */
class MclUrenSearchPage extends ObjectSearchPage {
function &getFilterFormPart() {
$part =& parent::getFilterFormPart();

$part->setImplicitCombiFilter(); //parameter missing
//should have passed an instance of PntSqlCombiFilter

return $part;
}

Output from development server:

E_WARNING: 'Missing argument 1 for
PntFilterFormPart::setImplicitCombiFilter(), called in
C:\metaclass\websites\@ndere\webtoko\classes\mcl\p roject\classMclUrenSearchPage.php
on line 9 and defined' in
C:\metaclass\websites\@ndere\webtoko\classes\pnt\w eb\parts\classPntFilterFormPart.php
at line 585
Request params:
'pntType'=>'Uren',
'pntHandler'=>'SearchPage',
'pntScd'=>'d',
'PHPSESSID'=>'66381c07e127a5ab7e3309dc27598741'

class function line
-----------------------------------------------------------
PntFilterFormPart setImplicitCombiFilter
MclUrenSearchPage getFilterFormPart 9
PntObjectSearchPage getRequestedObject 75
PntObjectIndexPage initForHandleRequest 41
PntPage handleRequest 122
PntSite forwardRequest 203
array('pntType'=>'Uren', 'pntHandler'=>'SearchPage', 'pntScd'=>'d',
'PHPSESSID'=>'66381c07e127a5ab7e3309dc27598741')

PntSite handleRequest 194
- - 5 project\index.php
BTW, passing objects by reference is standard procedure in php4. It
excludes the use of defaults.

Greetings,

Henk Verhoeven,
www.phpPeanuts.org.

[pangea33]

On Jul 10, 3:40 pm, Henk verhoeven <news1@phpPeanuts_RemoveThis.org>
wrote:

lawrence k wrote:

How do others handle default parameter values?

I guess you mean "how do others handle missing parameters?"

Well, on the development server my error handler will produce a walkback
so that i can see where the call was coming from.

Example:

/** class of the user interface component being called upon
class PntFilterFormPart extends PntPagePart {

*// function that will be called */
function setImplicitCombiFilter(&$combiFilter) {

(....)

/** Front controller class /*
class Site extends PntSite {

function setErrorHandler() {
includeClass('ErrorHandler');
$this->errorHandler =& new ErrorHandler();
$this->errorHandler->startHandling();
}

(....)

/* class of the actual controller producing the requested page, contais
the errorneous call */
class MclUrenSearchPage extends ObjectSearchPage {
function &getFilterFormPart() {
$part =& parent::getFilterFormPart();

$part->setImplicitCombiFilter(); //parameter missing
//should have passed an instance of PntSqlCombiFilter

return $part;

}

Output from development server:

E_WARNING: 'Missing argument 1 for
PntFilterFormPart::setImplicitCombiFilter(), called in
C:\metaclass\websites\@ndere\webtoko\classes\mcl\p roject\classMclUrenSearchPage.php
on line 9 and defined' in
C:\metaclass\websites\@ndere\webtoko\classes\pnt\w eb\parts\classPntFilterFormPart.php
at line 585
Request params:
'pntType'=>'Uren',
'pntHandler'=>'SearchPage',
'pntScd'=>'d',
'PHPSESSID'=>'66381c07e127a5ab7e3309dc27598741'

class function line
-----------------------------------------------------------
PntFilterFormPart setImplicitCombiFilter
MclUrenSearchPage getFilterFormPart 9
PntObjectSearchPage getRequestedObject 75
PntObjectIndexPage initForHandleRequest 41
PntPage handleRequest 122
PntSite forwardRequest 203
array('pntType'=>'Uren', 'pntHandler'=>'SearchPage', 'pntScd'=>'d',
'PHPSESSID'=>'66381c07e127a5ab7e3309dc27598741')

PntSite handleRequest 194
- - 5 project\index.php

BTW, passing objects by reference is standard procedure in php4. It
excludes the use of defaults.

Greetings,

Henk Verhoeven,www.phpPeanuts.org.

There was a lot of good feedback in this thread, and I am not the sort
of self-absorbed developer who is closed to the viewpoints of others.
A lot of you have made me rethink portions of my original post. Thanks
for keeping it clean and for giving some alternatives rather than
simply bashing. Hopefully some others will weigh in on the subject too.

[lawrence k]

On Jul 7, 10:12 pm, gosha bine <[e-mail]:

pangea33 wrote:

My post got longer and longer as my thoughts came together on this
subject. The gist of my claim is that you shouldn't build something as
FRAGILE as a function that breaks if there are argument variations,
when you can simply build a more robust function in the first place.

If something is going to fail, let it fail. The sooner it fails, the
more chances to discover and fix the bug.

That's an interesting reply. Do you do any error checking at all in
your code? If so, what do you error check for?

[R. Rajesh Jeba Anbiah]

On Jul 7, 2:35 am, lawrence k <[e-mail]:

I'm working in PHP 4. Even if a parameter is mandatory, I nearly
always give it a default value of "false". Then I print an error
message if someone who is calling my function forgot the mandatory
parameter:

function outputHtmlToShowFile($fileName=false) {
if ($fileName) {
// code goes here
} else {
echo "In outputHtmlToShowAFile() the code expected the first
parameter to be a file name, but instead the value was false";
}

}

How do others handle default parameter values?

I've been avoiding this:

function outputHtmlToShowFile($fileName) { }

because if I do this and someone forgets to pass a file name to the
function, then the PHP parser issues an error. I've been assuming
that relying on the PHP parser to write my error messages for me is
unprofessional. Does anyone else feel that way?

IMHO, the default parameters options are for handling the
situation to have default values; it's not meant to professionally
handle exception of missing params.

If you define a function with default params in it, it would
usually mean that the function can be called without any params for
it's default behavior. So, if you want to handle missing params, use
exception/error handler.

--
<?php echo 'Just another PHP saint'; ?>
Email: rrjanbiah-at-Y!com Blog: http://rajeshanbiah.blogspot.com/