php trait using another trait

Question

I have a trait which is using another trait, and now I'm getting errors about functions that don't exist in classes. I have simplified the code:

settings.php:

<?php
trait settings{
    protected function getSetting($type, $setting){ // read setting from config.ini
        try{
            $configFile=dirname(__FILE__)."/../config.ini";
            if(!file_exists($configFile)||!is_file($configFile))throw new Exception("Config file was not found. ");
            $configContents=parse_ini_file($configFile,true);
            if(is_array($configContents)&&array_key_exists($type,$configContents)&&is_array($configContents[$type])&&array_key_exists($setting,$configContents[$type]))return $configContents[$type][$setting];
            else throw new Exception("Setting ".$setting." could not be found in ".$type.".");
        }
        catch(Exception $e){throw new Exception($e->getMessage());}
    }
}
?>

database.php

<?php
trait database{
    use settings,session;
    private $pdo;
    protected function connect(){ // connect to database
        try{
            $this->pdo=new PDO("mysql:host=".$this->getSetting("db","host").";dbname=".$this->getSetting("db","database"),$this->getSetting("db","user"),$this->getSetting("db","password"));
            $this->init();
        }
        catch(PDOException $e){throw new Exception($e->getMessage());}
    }
}
?>

users.php

<?php
class users{
    use database;
    public function __construct(){
        try{
            $this->connect();
        }
        catch(Exception $e){throw new Exception($e->getMessage());}
    }
    public function __destruct(){
        unset($this);
    }
    public function isAdmin(){
        try{
            if($this->loginStatus()===true){

            }
            else return false;
        }
        catch(Exception $e){throw new Exception($e->getMessage());}
    }
    public function loginStatus(){
        if(!$this->getSession("tysus")||!$this->getSession("tyspw"))return false;// user is not logged in because we couldn't find session with username and/or password
        if(!$this->userExists($this->getSession("tysus"),$this->getSession("tyspw")))return false;// user is unknown to database
        return true;// other checks failed, user must be logged in
    }
}
?>

And now I'm getting this error:

Fatal error: Call to undefined method users::readSetting() in /home/deb2371/domains/nonamenohistory.com/public_html/include/classes/class.database.php on line 18

What I thought would happen was something like this: Class users uses trait database and trait database would use trait settings and trait session.

If that was the case, I wouldn't get any errors, but unfortunately this isn't the case.

Does someone know how to fix this problem?

Because, besides making huge mess regarding violations of SOLID principles, they also are actually implemented (under the hood) as interpreter-assisted copy-paste. — tereško, Dec 23 '13 at 21:09
Furthermore, why catch an exception just to throw a new exception with the same message? — Justin E, Jul 26 '14 at 17:37
Can you please update your question that it IS possible so we do not waste time on reading about a syntax error? ;) — Daniel, Mar 25 '19 at 09:57

score 40 · Answer 1 · answered Apr 26 '18 at 07:17

Code reuse is one of the most important aspects of object-oriented programming.

A simple example of Multiple Traits and Composing Multiple Traits by which you can easily analyse you situation.

Using multiple traits

A class can use multiple traits. The following example demonstrates how to use multiple traits in the IDE class. It simulates the C compilation model in PHP for the sake of demonstration.

<?php

 trait Preprocessor{
 function preprocess() {
    echo 'Preprocess...done'. '<br/>';
  }
}
trait Compiler{
function compile() {
   echo 'Compile code... done'. '<br/>';
  }
}

trait Assembler{
function createObjCode() {
   echo 'Create the object code files... done.' . '<br/>';
 }
}

trait Linker{
function createExec(){
   echo 'Create the executable file...done' . '<br/>';
  }
}

class IDE{
use Preprocessor, Compiler, Assembler, Linker;

function run() {
 $this->preprocess();
 $this->compile();
 $this->createObjCode();
 $this->createExec();

  echo 'Execute the file...done' . '<br/>';
 }
}
$ide = new IDE();
$ide->run();

Composing multiple traits

A trait can be composed of other traits by using the use statement in the trait’s declaration. See the following example:

<?php

trait Reader{
public function read($source){
   echo sprintf("Read from %s <br/>",$source);
  }
}

trait Writer{
public function write($destination){
   echo sprintf("Write to %s <br/>",$destination);
  }
}

trait Copier{
use Reader, Writer;
public function copy($source,$destination){
   $this->read($source);
   $this->write($destination);
 }
}

class FileUtil{
use Copier;
public function copyFile($source,$destination){
   $this->copy($source, $destination);
 }
}

Clearly, considering the generic title on this question, this answer will be the correct one for 99% of visitors. Thanks for the nice detailed examples! (in my case, I only wound up here because of a "syntax error" of my own, but your examples clarified I had my traits configured right, and I found the problem, as predicted) — jerclarke, Feb 14 '22 at 22:02
Is `class FileUtil { use Reader; use Copier; … }` (with `Copier` already containing `Reader`) an error, or what is happening then? — luckydonald, Dec 08 '22 at 12:31
@luckydonald - Can you put down the error in your case here. — Mohd Belal, Dec 11 '22 at 09:17
I was asking if it works. From what I've seen it actually isn't an error, and it works to include the same trait twice. — luckydonald, Jan 04 '23 at 16:17

score 21 · Accepted Answer · answered Dec 23 '13 at 14:56

21

Maybe because readSetting is actually called getSetting ?

answered Dec 23 '13 at 14:56

Noino

593
4
13

php trait using another trait

2 Answers2

Linked

Related