Is there Java HashMap equivalent in PHP?

Arrays in PHP can have Key Value structure.

Create a Java like HashMap in PHP with O(1) read complexity.

Open a phpsh terminal:

php> $myhashmap = array();
php> $myhashmap['mykey1'] = 'myvalue1';
php> $myhashmap['mykey2'] = 'myvalue2';
php> echo $myhashmap['mykey2'];
myvalue2

The complexity of the $myhashmap['mykey2'] in this case appears to be constant time O(1), meaning that as the size of $myhasmap approaches infinity, the amount of time it takes to retrieve a value given a key stays the same.

Evidence the php array read is constant time:

Run this through the PHP interpreter:

php> for($x = 0; $x < 1000000000; $x++){
 ... $myhashmap[$x] = $x . " derp";
 ... }

The loop adds 1 billion key/values, it takes about 2 minutes to add them all to the hashmap which may exhaust your memory.

Then see how long it takes to do a lookup:

php> system('date +%N');echo "  " . $myhashmap[10333] . "  ";system('date +%N');
786946389  10333 derp  789008364

So how fast is the PHP array map lookup?

The 10333 is the key we looked up. 1 million nanoseconds == 1 millisecond. The amount of time it takes to get a value from a key is 2.06 million nanoseconds or about 2 milliseconds. About the same amount of time if the array were empty. This looks like constant time to me.

Depending on what you want you might be interested in the SPL Object Storage class.

http://php.net/manual/en/class.splobjectstorage.php

It lets you use objects as keys, has an interface to count, get the hash and other goodies.

$s = new SplObjectStorage;
$o1 = new stdClass;
$o2 = new stdClass;
$o2->foo = 'bar';

$s[$o1] = 'baz';
$s[$o2] = 'bingo';

echo $s[$o1]; // 'baz'
echo $s[$o2]; // 'bingo'