Converting Java hashmap initializer to PHP equivalent

Question

Just curious which way is correct?

// the origional JAVA method
public void setRequestHeader(String key, String value) {
    if (this.headers == null) {
        this.headers = new HashMap<String, String>();
    }
    this.headers.put(key, value);
}

should this be interpreted in PHP as

Class HashMap {}

/**
 * @return this
 */
public function setRequestHeader($key, $value) {
    if ($this->headers == NULL) {
        $this->headers = new HashMap();
    }
    return $this->headers->$key = $value;
}

....or....

/**
 * @return array
 */
public function setRequestHeader($key, $value) {
    if ($this->headers == NULL) {
        $this->headers = array();
    }
    return $this->headers[$key] = $value;
}

if the associative array is correct like I believe, would there be a need for declaring this variable at the top of the class?

// JAVA version
private HashMap<String, String> headers;

Would be akin to

// PHP version
private $headers = array();

For your second question, you don't need to declare something as an array before using it in PHP, so no, there isn't a "need" for it. It's probably better practice though. — Tushar
– Tushar, Commented Mar 18, 2013 at 22:19
Yeah it would change the second method (the associative one) to ask if(empty($this->headers)) // do stuff instead of if ... == NULL — ehime
– ehime, Commented Mar 18, 2013 at 22:22

Community · Accepted Answer · 2017-05-23 11:50:09Z

2

Arrays in PHP have a key-value structure...thus is correct:

$this->headers[$key] = $value;

In fact, the PHP manual says:

An array in PHP is actually an ordered map.

http://php.net/manual/de/language.types.array.php

Although, according to How is the PHP array implemented on the C level? , it is actually a HashTable, which means you can rely on the O(1) lookup.

edited May 23, 2017 at 11:50

CommunityBot

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answered Mar 18, 2013 at 22:12

Tushar

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3 Comments

ehime Over a year ago

+1. I also believe this is correct, but wanted to see if anyone doesn't believe that associative arrays are PHP's equivalent of hashmaps and why. The only reason I ask is that this is in a Class related OOP scenario.

Tushar Over a year ago

@ehime Fair enough. I figured you knew the ordered map bit, but I was surprised as well to read that they were implemented as a HashTable. Maybe this will be interesting to others as well :)

ehime Over a year ago

Yeah I thought that this particular scenario interesting enough to be worth asking about?

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