preg_replace_callback() - Callback inside current object instance

Question

Warning: preg_replace_callback() [function.preg-replace-callback]: Requires argument 2, 'info', to be a valid callback in [...]

public function getDisplay(){
    $info = array_merge($this->info,array());

    return  preg_replace_callback('!\{\{(\w+)\}\}!', 'info', $this->display);
}

In a public function from "MyClass", stopped working when I moved from another class to this one. Which was:

public function getEdit( $type){
    $all_info = $this->info;

    return preg_replace_callback('!\{\{(\w+)\}\}!', 'all_info', $edit_contents);
}

Both are cleaned up, and now I can't retest with previous class because it's already long gone.

I'm sure using variables is not allowed, but it was working, so I'm clueless.

When I do this, as suggested in some stackoverflow thread, but obviously it's not made to be used within objects:

public function getDisplay(){
    $display_info = $this->info;

    function display_info($matches) {
        global $display_info;
        return $display_info[$matches[1]];
    }

    return  preg_replace_callback('!\{\{(\w+)\}\}!', 'display_info', $this->display);
}

So I need some love and guidance cuz php is driving me crazy this week...

Tadeck · Accepted Answer · 2012-08-07 07:35:24Z

14

Instead of using anonymous functions or more complex methods, you can just use one of methods supported for passing callbacks (see the documentation on callbacks):

A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1.

To pass "info" method of current object as a callback, just do the following:

array($this, 'info')

and pass it wherever you want to use "info" method as a callback within one of the objects other methods.

answered Aug 7, 2012 at 7:35

Tadeck

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1 Comment

Ben Over a year ago

+1 IMO this is the correct way to do it, in other functions which have callbacks as well. Closures seem a bit...cramped, frantic.

DaveRandom · Accepted Answer · 2012-06-23 00:12:24Z

4

The correct way to do this would be with a closure:

public function getDisplay() {

    // While $this support in closures has been recently added (>=5.4.0), it's
    // not yet widely available, so we'll get another reference to the current
    // instance into $that first:
    $that = $this;

    // Now we'll write that preg... line of which you speak, with a closure:
    return  preg_replace_callback('!\{\{(\w+)\}\}!', function($matches) use($that) {
        return $that->info[$matches[1]];
    }, $this->display);

}

edited Jun 23, 2012 at 0:12

answered Jun 22, 2012 at 21:56

DaveRandom

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6 Comments

localhost Over a year ago

That is soo bootyfull!! Way too nice to not be used! But my version is 5.3.x Damn that Wamp!

DaveRandom Over a year ago

5.3 is fine for the above code, it's just if you are 5.2 or less that closures don't work.

DaveRandom Over a year ago

The 5.4 constraint is just for using the magic variable $this within a closure, which is why I created $that. The one issue with this is that the property info will need to be public.

localhost Over a year ago

This would be nice: function($matches) use($that) { return $that->getInfo()[$matches[1]]. But if I remember correctly PHP disallows that...

DaveRandom Over a year ago

@localhost That syntax is known as array dereferencing and it works as of 5.4. No dice if you're stuck with 5.3 though.

|

localhost · Accepted Answer · 2012-06-22 21:46:07Z

2

This solved it:

public function getDisplay(){
    return  preg_replace_callback('!\{\{(\w+)\}\}!', array(get_class($this), '_preg_replace_callback'), $this->display);
}

private function _preg_replace_callback($matches){
    return $this->info[$matches[1]];
}

I did try this approach before, but didn't use the get_class() function to wrap $this. Oh bother...

answered Jun 22, 2012 at 21:46

localhost

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2 Comments

goat Over a year ago

you shouldn't need get_class(). array($this, '_preg_replace_callback') is ok. actually, i don't think your posted solution can work.

localhost Over a year ago

well it did work, and wasn't working without get_class()...It's PHP, go figure...

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