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Defining a callback Func for preg_replace_ca llback(), within some class's method

Hi,

I'm trying to use preg_replace_ca llback within a method. The
preg_replace_ca llback() & mycallback() pair will only be used by this
method, and this method will probably only be called once in the
object's lifetime (so there's no sense in making the callback function
a method of the class...(is there??))

Instead, I wanted to use create_function () to create a make-shift
callback function within the method. (seeing as you can't define a
function within a method). However, it needs to be able to access a
property (or its getter) of the object, and it complains that it's not
within the right scope to access it.

What's the best way of doing this?

class myclass {
....
function mycallback($mat ches){
return $this->properties[$matches[1]]
}
function mymethod ($subject){
$mystr = preg_replace_ca llback(
"!{([a-z]+)}!",
array($this,'my callback'),
$subject
)
}
....
}

This above is the only way I've found of making this work so far.
However, mycallback() I really don't think should have the scope it
does, i would like its definition to stay constrained to mymethod().
any ideas would be greatly appreaciated!

Jody

Jan 16 '06 #1
8 4480
What you're trying to do is create a closure, which can't be done in
PHP as far as I know.

Jan 17 '06 #2
d
<jo**********@g mail.com> wrote in message
news:11******** *************@g 43g2000cwa.goog legroups.com...
Hi,

I'm trying to use preg_replace_ca llback within a method. The
preg_replace_ca llback() & mycallback() pair will only be used by this
method, and this method will probably only be called once in the
object's lifetime (so there's no sense in making the callback function
a method of the class...(is there??))

Instead, I wanted to use create_function () to create a make-shift
callback function within the method. (seeing as you can't define a
function within a method). However, it needs to be able to access a
property (or its getter) of the object, and it complains that it's not
within the right scope to access it.

What's the best way of doing this?

class myclass {
...
function mycallback($mat ches){
return $this->properties[$matches[1]]
}
function mymethod ($subject){
$mystr = preg_replace_ca llback(
"!{([a-z]+)}!",
array($this,'my callback'),
$subject
)
}
...
}
Have you tried using the create_function property? If you read the
documentation page for preg_replace_ca llback (*ahem*), you'll see an example
:)

http://uk.php.net/manual/en/function...e-callback.php
This above is the only way I've found of making this work so far.
However, mycallback() I really don't think should have the scope it
does, i would like its definition to stay constrained to mymethod().
any ideas would be greatly appreaciated!

Jody

Jan 17 '06 #3
index.php:
<?php
class myclass {
protected $vars = array();
function addVar($name,$v al){ $this->vars[$name] = $val; }
function output(){
$fileContents = file_get_conten ts("my.template ");
$outputString = preg_replace_ca llback(
'@{([A-Z]+)}@',
create_function ('$matcharray', 'return
$this->vars[$matches[1]];'),
$fileContents);
echo $outputString;
} }
$obj = new myclass();
$obj->addVar("NAME ", "bob");
$obj->addVar("MOBILE ", "0207 PHP RULES");
$obj->addVar("EMAIL" , "bo*@bob.co m");
$obj->output();
?>

my.template :
<ul>
<li>{NAME}</li>
<li>{MOBILE}</li>
<li>{EMAIL}</li>
</ul>

It produces the error:

Fatal error: Using $this when not in object context in
/www/thisproblem/index.php(10) : runtime-created function on line 1

In the example at
http://uk.php.net/manual/en/function...e-callback.php

They're not implementing a callback function with create_function () in
a class context, as opposed to my example above.

I'm still quite at a loss myself. I'm hazy on my lambda calculus but
surely there's a way round this?

--
J Florian

Jan 17 '06 #4
example.php:
<?php
class myclass {
protected $vars = array();
function addVar($name,$v al){ $this->vars[$name] = $val; }
function output(){
$fileContents = file_get_conten ts("my.template ");
$outputString = preg_replace_ca llback(
'@{([A-Z]+)}@',
create_function ('$matcharray', 'return
$this->vars[$matches[1]];'),
$fileContents);
echo $outputString;
} }

$obj = new myclass();
$obj->addVar("NAME ", "bob");
$obj->addVar("MOBILE ", "0207 PHP RULES");
$obj->addVar("EMAIL" , "b...@bob.com") ;
$obj->output();
?>

my.template :
<ul>
<li>{NAME}</li>
<li>{MOBILE}</li>
<li>{EMAIL}</li>
</ul>

It produces the error:

Fatal error: Using $this when not in object context in
/www/thisproblem/example.php(10) : runtime-created function on line 1

In the example at
http://uk.php.net/manual/en/function...e-callback.php

They're not implementing a callback function with create_function () in
a class context, as opposed to my example above.

Since it's a) not wise and b) not possible to declare a function within
a method (since it would be re-declared each time the method's used)
I'm still quite at a loss myself

I'm hazy on my lambda calculus but surely there's a way round this,
other than creating a method solely as a one-off callback?

Cheers

--
J Florian

Jan 17 '06 #5
jo**********@gm ail.com wrote:

They're not implementing a callback function with create_function () in
a class context, as opposed to my example above.

Since it's a) not wise and b) not possible to declare a function within
a method (since it would be re-declared each time the method's used)
I'm still quite at a loss myself

I'm hazy on my lambda calculus but surely there's a way round this,
other than creating a method solely as a one-off callback?


Given it a rest. Like I said, PHP does not have built-in support for
closure. It's possible to implement a closure class, of course. But
then you end up with an additional class floating around instead of a
method.

If you hate having an extra method that much, just have the method call
itself and branch based on the parameter passed. Example:

function output($param = null){
if($param) {
}
else {
$outputString = preg_replace_ca llback( ... array($this,
'output') ... );
}
}

Jan 17 '06 #6
On 16 Jan 2006 17:40:31 -0800, "Chung Leong" <ch***********@ hotmail.com> wrote:
What you're trying to do is create a closure, which can't be done in
PHP as far as I know.


create_function () gets close to this.

--
Andy Hassall :: an**@andyh.co.u k :: http://www.andyh.co.uk
http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool
Jan 17 '06 #7

Andy Hassall wrote:
On 16 Jan 2006 17:40:31 -0800, "Chung Leong" <ch***********@ hotmail.com> wrote:
What you're trying to do is create a closure, which can't be done in
PHP as far as I know.


create_function () gets close to this.

--
Andy Hassall :: an**@andyh.co.u k :: http://www.andyh.co.uk
http://www.andyhsoftware.co.uk/space :: disk and FTP usage analysis tool


There is no good way to bind a reference to the function though, aside
from (a) a variable global (b) a wrapper class plus the array($obj,
'function') construct. PHP evidently doesn't allow lambda functions to
have static variable, so you can't give a function a private variable.

Jan 18 '06 #8
>> Given it a rest

lol. I will. I've been convinced.

Thanks for everyone's help

Jan 18 '06 #9

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