How to reference constructed variables from a dynamically added function - php

Question

How would one rewrite the following ...
class crunch {
private $funcs = [];
public function set($name, $function) {
$this->funcs[$name] = $function;
}
public function call($function, $data=false) {
if (isset($this->funcs[$function]) && is_callable($this->funcs[$function])) {
return $this->funcs[$function]($data);
}
}
}
$db = 'dbhandle';
$crunch = new crunch();
$crunch->set('myfunction', function($data) {
global $db;
echo 'db = '. $db .'<br>'. json_encode( $data );
});
$crunch->call('myfunction', [123,'asd']);
... which correctly outputs ...
db = dbhandle
[123,"asd"]
... to remove the ugly global requirement when using frequently used variables/handles within dynamically added functions?
Normally, I'd define the global on construction as follows, but this understandably fails with the fatal error Uncaught Error: Using $this when not in object context ...
class crunch {
private $db;
private $funcs = [];
public function __construct($db) {
$this->db = $db;
}
public function set($name, $function) {
$this->funcs[$name] = $function;
}
public function call($function, $data=false) {
if (isset($this->funcs[$function]) && is_callable($this->funcs[$function])) {
return $this->funcs[$function]($data);
}
}
}
$db = 'dbhandle';
$crunch = new crunch($db);
$crunch->set('myfunction', function($data) {
echo 'db = '. $this->db .'<br>'. json_encode( $data );
});
$crunch->call('myfunction', [123,'asd']);
What's the cleanest way to accomplish the goal?
EDIT: As #Rajdeep points out, I could pass $db within the $crunch->set() function. But I'd like to avoid this, since each dynamic function could reference anywhere from 0-5 of these private variables, and it would be inelegant to have to call all 5 with every $crunch->set().

Answer 1

Instead of creating a private instance variable $db, you could simply pass this variable to the call() method. Your code should be like this:
class crunch {
private $funcs = [];
public function set($name, $function) {
$this->funcs[$name] = $function;
}
public function call($function, $data=false, $db) {
if (isset($this->funcs[$function]) && is_callable($this->funcs[$function])) {
return $this->funcs[$function]($data, $db);
}
}
}
$db = 'dbhandle';
$crunch = new crunch();
$crunch->set('myfunction', function($data, $db){
echo 'db = '. $db .'<br>'. json_encode( $data );
});
$crunch->call('myfunction', [123,'asd'], $db);
Output:
db = dbhandle
[123,"asd"]
Update(1):
In case you want to access $db as instance variable only, the solution would be like this:
class crunch {
public $db;
private $funcs = [];
public function __construct($db) {
$this->db = $db;
}
public function set($name, $function) {
$this->funcs[$name] = $function;
}
public function call($function, $data=false) {
if (isset($this->funcs[$function]) && is_callable($this->funcs[$function])) {
return $this->funcs[$function]($this, $data);
}
}
}
$db = 'dbhandle';
$crunch = new crunch($db);
$crunch->set('myfunction', function($crunch, $data) {
echo 'db = '. $crunch->db .'<br>'. json_encode( $data );
});
$crunch->call('myfunction', [123,'asd']);
Note that you have to make $db as public member variable, otherwise it would be inaccessible while calling the set() method.