public function setCallback($env, callable $callable = null)
    {
        $this->swapCallable($env, $callable, $this->running_env);
        
        $this->callbacks[$env] = $callable;
        if (empty($this->errors[$env])) {
            $this->setCoreErrors($env, self::getDefaultCoreErrors());
        }
        if (empty($this->exceptions[$env])) {
            $this->setUncaughtExceptions($env, self::$default_exceptions);
        }
        
        return $this;
    }
public function setCallback($env, callable $callable = null)
    {
        $this->swapCallable($env, $callable, $this->running_env);
        
        $this->callbacks[$env] = $callable;
        if (empty($this->errors[$env])) {
            $this->setCoreErrors($env, self::getDefaultCoreErrors());
        }
        if (empty($this->exceptions[$env])) {
            $this->setUncaughtExceptions($env, self::$default_exceptions);
        }
        
        return $this;
    }
public function setCallback ( $ env , callable $ callable = null ) { $ this -> swapCallable ( $ env , $ callable , $ this -> running_env ) ; $ this -> callbacks [ $ env ] = $ callable ; if ( empty ( $ this -> errors [ $ env ] ) ) { $ this -> setCoreErrors ( $ env , self :: getDefaultCoreErrors ( ) ) ; } if ( empty ( $ this -> exceptions [ $ env ] ) ) { $ this -> setUncaughtExceptions ( $ env , self :: $ default_exceptions ) ; } return $ this ; }
Sets the callback that will be called when an error is handled

Uses the currently running environment when none is given.

Examples:
```php
$handler->setCallback(function($handler) {
// The $handler parameter is the ErrorHandler instance.
// The $handler->getLastError() method returns an exception which
// describes the error.
include("templates/error.php");
});

$handler->setCallback("live", function($handler) {
include("templates/error_live.php");
});

$handler->setCallback("dev", function($handler) {
include("templates/error_dev.php");
});
```

@param string|callable $env      Name of the environment
@param callable|null   $callable The error callback

@return $this
Sets the callback that will be called when an error is handled