I am trying to understand the idea behind ArrayAccess Interface,
I dont understand what each method is about, If those methods(functions) are "built in" functions and ArrayAccess Interface(also "built in") is only "make sure" i am going to implement those "built in" methods(functions)
I am trying to understand what does each of thoes functions is doing with our code "Behind the scenes".
function offsetSet($offset, $value);
function offsetGet($offset);
function offsetUnset($offset);
function offsetExists($offset);
If i understand ArrayAccess is a Built In interface that Containing seals to implement, when we implement them we only implement references to thoes built in functions, I will be happy if some one can please help me get this right.
If you implement that interface, then the object acts like an array. e.g., if $foo is an instance of a class that implements ArrayAccess:
$foo['bar'] = 42 calls offsetSet('bar', 42).
echo $foo['bar'] calls offsetGet('bar').
unset($foo['bar']) calls offsetUnset('bar').
isset($foo['bar']) calls offsetExists('bar').
You never explicitly call the functions offset* yourself. It happens implicitly when you access the object as an array.
While comparing ArrayAccess to SimpleXMLElement (an internal class not implementing it), I was curious, too. The interface is well documented in the manual already, so I wanted to highlight some differences in specific with offset types.
But first of all a boilerplate example implementation of a class implementing ArrayAccess giving output when accessed:
/**
* ArrayAccess Example
*/
class ExampleArrayLikeAccess implements ArrayAccess
{
/**
* Whether a offset exists
*
* @link http://php.net/manual/en/arrayaccess.offsetexists.php
* @param mixed $offset - An offset to check for.
* @return boolean true on success or false on failure.
*
* The return value will be casted to boolean if non-boolean was returned.
*/
public function offsetExists($offset) {
echo " - offsetExists(", $this->varString($offset),")\n";
}
/**
* Offset to retrieve
*
* @link http://php.net/manual/en/arrayaccess.offsetget.php
* @param mixed $offset The offset to retrieve.
* @return mixed Can return all value types.
*/
public function offsetGet($offset) {
echo " - offsetGet(", $this->varString($offset),")\n";
}
/**
* Offset to set
*
* @link http://php.net/manual/en/arrayaccess.offsetset.php
* @param mixed $offset The offset to assign the value to.
* @param mixed $value The value to set.
* @return void
*/
public function offsetSet($offset, $value) {
echo " - offsetSet(", $this->varString($offset), ", ", $this->varString($value), ")\n";
}
/**
* Offset to unset
* @link http://php.net/manual/en/arrayaccess.offsetunset.php
* @param mixed $offset The offset to unset.
* @return void
*/
public function offsetUnset($offset) {
echo " - offsetUnset(", $this->varString($offset),")\n";
}
/**
* helper to give a variable dump in form of a string
*/
private function varString($var) {
ob_start();
var_dump($var);
return trim(strtr(ob_get_clean(), ["\n" => '', "\r" => '']), ' {}');
}
}
Running some usage-examples with it. I have left notes in form of comments. It should be pretty self-explaining:
$like = new ExampleArrayLikeAccess();
/* offsetExists */
// indexes/keys that behave similar to PHP arrays:
isset($like[1]); # integer stay integer
# offsetExists(int(1))
isset($like['1']); # string like an integer - converted to integer
# offsetExists(int(1))
isset($like['01']); # string unlike an integer - stays string
# offsetExists(string(2) "01")
isset($like[TRUE]); # booleans are converted to integer
# offsetExists(bool(true))
// indexes/keys that differ to PHP arrays:
isset($like[1.1]); # a float stays a float (double)
# offsetExists(double(1.1))
isset($like[NULL]); # NULL stays NULL
# offsetExists(NULL)
isset($like[array()]); # array stays array
# offsetExists(array(0))
isset($like[$like]); # object stays object
# offsetExists(class SxeLikeAccess#2 (0))
/* offsetGet */
// indexes/keys behave the same as with offsetExists:
$like[1]; # offsetGet(int(1))
$like['1']; # offsetGet(int(1))
$like['01']; # offsetGet(string(2) "01")
// ...
/* offsetSet */
$like[1] = 'value'; # index/key behaves the same as with offsetExists
# offsetSet(int(1), string(5) "value")
$like[] = 'value'; # index/key is NULL
# offsetSet(NULL, string(5) "value")
$like[NULL] = 'value'; # index/key is NULL
# offsetSet(NULL, string(5) "value")
/* offsetUnset */
unset($like[1]); # index/key behaves the same as with offsetExists
unset($like[NULL]); # same for NULL
Key differences to standard PHP arrays are that you can use not only integer and string as offsets.
