ArrayList in php

Question

Are there any data structures in php other than array. Is it possible to create a data structure such as an ArrayList? If so please provide some references or some kind of implementation.

Answer 1

Everything you need to know about arrays can be found in the documentation.

All of the available functions for arrays are listed in the functions reference.

Some notes:

• Arrays were originally the only datastructure in PHP. That is why they are so flexible. They were meant to be used as stack, queue, array, list, hash table and so forth. Later on PHP introduced the spl Datastructures.
• Unlike Java, PHP is not a pure OO language. An array itself has no built in methods you can apply. This has to be done via "normal" functions.
• Arrays have no fixed size. They expand and shrink automatically.

In the following I tried to list the PHP alternatives for the most common ArrayList methods:

• add(element) is basically just appending via $array[] = $element. The new value gets the next free numeric index (this is the preferred way). You can also use array_push($array, $element).
• addAll(ArrayList): array_merge($array1, $array2) in a way. Be careful when merging associative arrays. Values for the same keys will be overwritten.

• clone(): As arrays are not objects, you "clone" an array by just assigning it to another variable:

      $a = array(1,2,3);     $b = $a; 

• contains(element): in_array($element, $array)

• get(index): Like in most languages: $val = $array[index];
• indexOf(element): array_keys($array, $element) with the value you search for as second parameter
• isEmpty(): empty($array)
• remove(index): Its unset($array[index])
• remove(value) with value: You have to get the keys first (see indexOf), iterate over they keys and use unset.
• size(): count($array)

Answer 2

I tried to implement, here's some simple code:

class ArrayList {  private $list = array();   public function Add($obj) {     array_push($this->list, $obj); }  public function Remove($key) {     if(array_key_exists($key, $this->list))     {         unset($this->list[$key]);     } }  public function Size() {     return count($this->list); }  public function IsEmpty() {     return empty($this->list); }  public function GetObj($key) {     if(array_key_exists($key, $this->list))     {         return $this->list[$key];     }     else     {         return NULL;     } }  public function GetKey($obj) {     $arrKeys = array_keys($this->list, $obj);      if(empty($arrKeys))         {         return -1;     }     else     {         return $arrKeys[0];     } }  }