A problem using an external class in Datatables Editor

obrienj

This problem may be due to an incomplete understanding of PHP but it files in the face of all the other programming languages I use and I need an explanation so I can use other external classes

I have an purpose defined class as follows:

<?php

namespace OTLogger;

class OTLogger {
 
    // Create a new constructor
    public function __construct() {
    }

    // write some text
    public function lwrite($message) {

        // do work here
        
    }
}

<?php
>
```
?>


And following is a shortened annotated Datatbles Editor PHP script.

<?php

error_reporting(E_ALL);
ini_set('display_errors', '1');

require( "C:/wamp64/www/distLibs/phpLibs/DataTables-Editor/DataTables.php" );

require( "C:/wamp64/www/distLibs/phpLibs/OTLogger.php" );

use
DataTables\Editor,
DataTables\Editor\Field,
DataTables\Editor\Format,
DataTables\Editor\Mjoin,
DataTables\Editor\Options,
DataTables\Editor\Upload,

use OTLogger\OTLogger;

$log = new OTLogger();

$log->lwrite("some text"); //<++++++++ this works

Editor::inst( $db, 'calendar.events', 'RID' )

->fields(
    Field::inst( 'RID' )->set(false),                           
    Field::inst( 'id' ),
    Field::inst( 'title' )->validator( 'Validate::notEmpty' ),
)

->on( 'preCreate',
    function ( $editor, $values ) {
        $log->lwrite("some text");           //<++++++++ this fails with because $log is null
    })

->on( 'postCreate',
    function ( $editor, $id, $values, $row ) {
        $log = new OTLogger();
        $log->lwrite("some text");          //<++++++++ this works because $log is instantiated locally

    })

->process( $_POST )

->json();

```

Put simply. I am trying to produce a "global $log" that can be accessed anywhere like I would in C, C++, javascript, Java, C# and other languages.

Clearly I have either made an error I can't find or there is something in the structure of PHP or Datatables editor that I don't understand.

All help appreciated.

Regards,
Jim

tangerine

It's a scoping issue.
You have answered your own question, really:

$log->lwrite("some text");          //<++++++++ this works because $log is instantiated locally

In the previous instance ( preCreate() ) $log is not "visible".

My own uses of Editor would usually be inside a class:

class TableToEdit {
protected $log;          // In your case you might have this.

public function doStuff() {
$this->log = new OTLogger();  // In your case...

// Now initialise Editor, and you can use $this->log 
//    in preCreate() and any other function of this class.
}
}

allan

PHP's scoping of variables does fly in the face of all other programming languages for anonymous functions. I'm going to write a tech note up about it since, although it isn't specifically a DataTables issue, is does keep cropping up as a question.

To use a variable inside an anonymous function, you have to use the use statement (PHP documentation):

function ( $editor, $values ) use ( $log ) {

Its bonkers if you are used to Javascript or C#, but that's how it works in PHP.

The other option is to do as @tangerine says and create a new instance in the function.

Allan

obrienj

Allan,

I like your answer and I read the PHP doc, but to show my complete ignorance of this area of PHP, using my example above where exactly do I put the "use"?

I learned very early in my career (50-some years) that techo-religious debates about programming languages, operating systems, and other such things are pointless. One uses the tool that is available and if that requires a big shift in thinking, so be it , it comes with the territory so please don't mis-understand my comments..

Regards,
Jim

allan

Replace:

function ( $editor, $values ) {

with

function ( $editor, $values ) use ( $log ) {

That should be all that is needed.

Allan