Does PHP have built-in data structures?

Question

I\'m looking at the PHP Manual, and I\'m not seeing a section on data structures that most languages have, such as lists and sets. Am I just blind or does PHP not have anything

Answer 1

You can always create your own if you don't feel PHP includes a specific type of data structure. For example, here is a simple Set data structure backed by an Array.

ArraySet: https://github.com/abelperez/collections/blob/master/ArraySet.php

class ArraySet
{
    /** Elements in this set */
    private $elements;

    /** the number of elements in this set */
    private $size = 0;

    /**
     * Constructs this set.
     */ 
    public function ArraySet() {
        $this->elements = array();
    }

    /**
     * Adds the specified element to this set if 
     * it is not already present.
     * 
     * @param any $element
     *
     * @returns true if the specified element was
     * added to this set.
     */
    public function add($element) {
        if (! in_array($element, $this->elements)) {
            $this->elements[] = $element;
            $this->size++;
            return true;
        }
        return false;
    }

    /**
     * Adds all of the elements in the specified 
     * collection to this set if they're not already present.
     * 
     * @param array $collection
     * 
     * @returns true if any of the elements in the
     * specified collection where added to this set. 
     */ 
    public function addAll($collection) {
        $changed = false;
        foreach ($collection as $element) {
            if ($this->add($element)) {
                $changed = true;
            }
        }
        return $changed;
    }

    /**
     * Removes all the elements from this set.
     */ 
    public function clear() {
        $this->elements = array();
        $this->size = 0;
    }

    /**
     * Checks if this set contains the specified element. 
     * 
     * @param any $element
     *
     * @returns true if this set contains the specified
     * element.
     */ 
    public function contains($element) {
        return in_array($element, $this->elements);
    }

    /**
     * Checks if this set contains all the specified 
     * element.
     * 
     * @param array $collection
     * 
     * @returns true if this set contains all the specified
     * element. 
     */ 
    public function containsAll($collection) {
        foreach ($collection as $element) {
            if (! in_array($element, $this->elements)) {
                return false;
            }
        }
        return true;
    }

    /**
     * Checks if this set contains elements.
     * 
     * @returns true if this set contains no elements. 
     */ 
    public function isEmpty() {
        return count($this->elements) <= 0;
    }

    /**
     * Get's an iterator over the elements in this set.
     * 
     * @returns an iterator over the elements in this set.
     */ 
    public function iterator() {
        return new SimpleIterator($this->elements);
    }

    /**
     * Removes the specified element from this set.
     * 
     * @param any $element
     *
     * @returns true if the specified element is removed.
     */ 
    public function remove($element) {
        if (! in_array($element, $this->elements)) return false;

        foreach ($this->elements as $k => $v) {
            if ($element == $v) {
                unset($this->elements[$k]);
                $this->size--;
                return true;
            }
        }       
    }

    /**
     * Removes all the specified elements from this set.
     * 
     * @param array $collection
     *
     * @returns true if all the specified elemensts
     * are removed from this set. 
     */ 
    public function removeAll($collection) {
        $changed = false;
        foreach ($collection as $element) {
            if ($this->remove($element)) {
                $changed = true;
            } 
        }
        return $changed;
    }

    /**
     * Retains the elements in this set that are
     * in the specified collection.  If the specified
     * collection is also a set, this method effectively
     * modifies this set into the intersection of 
     * this set and the specified collection.
     * 
     * @param array $collection
     *
     * @returns true if this set changed as a result
     * of the specified collection.
     */ 
    public function retainAll($collection) {
        $changed = false;
        foreach ($this->elements as $k => $v) {
            if (! in_array($v, $collection)) {
                unset($this->elements[$k]);
                $this->size--;
                $changed = true;
            }
        }
        return $changed;
    }

    /**
     * Returns the number of elements in this set.
     * 
     * @returns the number of elements in this set.
     */ 
    public function size() {
        return $this->size; 
    }

    /**
     * Returns an array that contains all the 
     * elements in this set.
     * 
     * @returns an array that contains all the 
     * elements in this set.
     */ 
    public function toArray() {
        $elements = $this->elements;
        return $elements;   
    }
}