Use a trait conditionally in PHP

You can create a class with use T which extends the class without use T. And then in your code where you use the class do an if and instantiate the one or the other class.

<?php

trait T {
}

class A {
}

class B extends A {
    use T;
}

// In an other part of code
$obj = null;

if($condition) {
    $obj = new B();
} else {
    $obj = new A();
}

/* EOF */

As long as your condition can be evaluated at the class root, you can do the following:

if (<condition here>) {
    class BaseFoo
    {
        use FooTrait;
    }
} else {
    class BaseFoo {
    }
}

class Foo extends BaseFoo
{
    // common properties
}

You can outsource your conditional code (like debug-functions) in a trait and do something like that.

//your Trait

if($isModeDbg){
    trait Dbg{
        function dbg(mssg){
            debugbarOrSomethingSimilar(mssg);
        }
    }
}else{
    trait Dbg{
        function dbg(mssg){
        }
    }
}

//your class
class Something{
  use Dbg;
}