Is there Java HashMap equivalent in PHP?

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I need PHP object similar to HashMap in Java, but I didn't find when I googled, so if someone knows how I can mimic HashMaps in PHP, help would be appreciated.

Answers

Arrays in PHP can have Key Value structure.

Saturday, August 27, 2022

linoyasdi-8d90f14cc77c

Dictionary is probably the closest. System.Collections.Generic.Dictionary implements the System.Collections.Generic.IDictionary interface (which is similar to Java's Map interface).

Some notable differences that you should be aware of:

Adding/Getting items
- Java's HashMap has the put and get methods for setting/getting items
  - myMap.put(key, value)
  - MyObject value = myMap.get(key)
- C#'s Dictionary uses [] indexing for setting/getting items
  - myDictionary[key] = value
  - MyObject value = myDictionary[key]
null keys
- Java's HashMap allows null keys
- .NET's Dictionary throws an ArgumentNullException if you try to add a null key
Adding a duplicate key
- Java's HashMap will replace the existing value with the new one.
- .NET's Dictionary will replace the existing value with the new one if you use [] indexing. If you use the Add method, it will instead throw an ArgumentException.
Attempting to get a non-existent key
- Java's HashMap will return null.
- .NET's Dictionary will throw a KeyNotFoundException. You can use the TryGetValue method instead of the [] indexing to avoid this:
  MyObject value = null; if (!myDictionary.TryGetValue(key, out value)) { /* key doesn't exist */ }

Dictionary's has a ContainsKey method that can help deal with the previous two problems.

Monday, September 19, 2022

james_hunt

In bytecode you have a nop instruction, but there's no nop statement in the Java language.

You can add an extra ; on a line by itself and the code will still compile, but that's not much more meaningful than adding an empty line.

Another "does nothing" statement could be:

assert true;

which has no side-effects what so ever, and can be turned off when executing the program.

As it turns out, assert true does not seem to generate any bytecode instructions, which causes break-points on assert true to be skipped all together. Eclipse is however able to break on a statement such as

assert Boolean.TRUE;

which is quite similar.

Tuesday, August 2, 2022

jon_anderson

Never used any of those, but they look interesting..

Take a look at Gearman as well.. more overhead in systems like these but you get other cool stuff :) Guess it depends on your needs ..

Friday, November 11, 2022

the_falvert

If for any String s crunch(s) returns a reproducible String that the attacker cannot guess, the DDoS attack has effectively been prevented right?

Basically, this is what you do when you salt password hashes (although for slightly different reasons). It doesn't prevent collision attacks entirely (if you have a hash function mapping arbitrary-length input to a fixed-length output, hashes can always collide), but using a secret salt should make such attacks harder.

A quick'n'dirty implementation could look something like this:

public class SaltedHashMap<V> {
    private final Map<String, V> map = new HashMap<>();
    private final String salt;
    public SaltedHashMap(String salt) {
        this.salt = salt;
    }
    public V get(String key){
        return map.get(key + salt);
    }
    public void put(String key, V value) {
        map.put(key + salt, value);
    }
}

Using a web server as an example, we could use a SecureRandom to randomize a new salt for every incoming request, meaning that even if you managed to figure out a collision-generating input for one request, it would be extremely unlikely to work for other requests.

Saturday, November 26, 2022

zika

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Is there Java HashMap equivalent in PHP?

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