Introduction
In PHP, ArrayAccess interface is used to develop a class that provides array like access to one of properties which is an array. Such array property may be manipulated without exposing it during object creation. ArrayAccess interface defines following abstract methods
Syntax
ArrayAccess { /* Methods */ abstract public offsetExists ( mixed $offset ) : bool abstract public offsetGet ( mixed $offset ) : mixed abstract public offsetSet ( mixed $offset , mixed $value ) : void abstract public offsetUnset ( mixed $offset ) : void }
Methods
ArrayAccess::offsetExists − Whether an offset exists
ArrayAccess::offsetGet − Offset to retrieve
ArrayAccess::offsetSet − Assign a value to the specified offset
ArrayAccess::offsetUnset − Unset an offset.
ArrayAccess Example
In following example, an associative array is internal private proprty of myclass. The key acts as offset. We can set, retieve and unset an item in the array. If offset is not given, it is treated as an integer, every time incrementing to next index.
Example
<?php class myclass implements ArrayAccess { private $arr = array(); public function __construct() { $this->arr = array( "Mumbai" => "Maharashtra", "Hyderabad" => "A.P.", "Patna" => "Bihar", ); } public function offsetSet($offset, $value) { if (is_null($offset)) { $this->arr[] = $value; } else { $this->arr[$offset] = $value; } } public function offsetExists($offset) { return isset($this->arr[$offset]); } public function offsetUnset($offset) { unset($this->arr[$offset]); } public function offsetGet($offset) { return isset($this->arr[$offset]) ? $this->arr[$offset] : null; } } $obj = new myclass(); var_dump(isset($obj["Mumbai"])); var_dump($obj["Mumbai"]); unset($obj["Mumbai"]); var_dump(isset($obj["Mumbai"])); $obj["Bombay"] = "Maharashtra"; var_dump($obj["Bombay"]); $obj["Chennai"] = 'Tamilnadu'; $obj[] = 'New State'; $obj["Hyderabad"] = 'Telangana'; print_r($obj); ?>
Output
Above program shows following output
bool(true) string(11) "Maharashtra" bool(false) string(11) "Maharashtra" myclass Object( [arr:myclass:private] => Array( [Hyderabad] => Telangana [Patna] => Bihar [Bombay] => Maharashtra [Chennai] => Tamilnadu [0] => New State ) )
The array property of class can also be an indexed array. In that case, index of element (starting from 0) acts as offset. When calling offsetSet(0 method without offset argument, index of array is incremented to next available integer
Example
<?php class myclass implements ArrayAccess { private $arr = array(); public function __construct() { $this->arr = array("Mumbai", "Hyderabad", "Patna"); } public function offsetSet($offset, $value) { if (is_null($offset)) { $this->arr[] = $value; } else { $this->arr[$offset] = $value; } } public function offsetExists($offset) { eturn isset($this->arr[$offset]); } public function offsetUnset($offset) { unset($this->arr[$offset]); } public function offsetGet($offset) { return isset($this->arr[$offset]) ? $this->arr[$offset] : null; } } $obj = new myclass(); var_dump(isset($obj[0])); var_dump($obj[0]); unset($obj[0]); var_dump(isset($obj[0])); $obj[3] = "Pune"; var_dump($obj[3]); $obj[4] = 'Chennai'; $obj[] = 'NewDelhi'; $obj[2] = 'Benguluru'; print_r($obj); ?>
Output
Above program shows following output
bool(true) string(6) "Mumbai" bool(false) string(4) "Pune" myclass Object( [arr:myclass:private] => Array( [1] => Hyderabad [2] => Benguluru [3] => Pune [4] => Chennai [5] => NewDelhi ) )