PHP internal hashCode Function

Question

I am looking for the PHP equelent to JAVA's

 "SomeString".hashCode();

function. The hashCode i am looking for should be the same which is used for indexing Hashmaps in PHP. I Hope you can help me :)

EDIT:

Okay found the function i was searching for its written in C and is not available in PHP itself but thanks for your help !

ulong zend_inline_hash_func(char *arKey, uint nKeyLength)
{
        ulong $h = 5381;
        char *arEnd = arKey + nKeyLength;

        while (arKey < arEnd) {
                $h += ($h << 5);
                $h += (ulong) *arKey++;
        }
        return $h;
}

Answer 1

Arkh and the github solution referenced by guiguoz are in the right direction, but both fail to take into account that PHP will upconvert the integer hash value to a double as soon as it exceeds 2^61. The java function, which is calculated using fixed hardware 32-bit signed values, involves 32-bit arithmetic overflow (intrinsic to the CPU) to keep the value as a 32-bit signed integer.

In PHP, you will need to manually perform that arithmetic overflow each time the $hash is updated:

function overflow32($v)
{
    $v = $v % 4294967296;
    if ($v > 2147483647) return $v - 4294967296;
    elseif ($v < -2147483648) return $v + 4294967296;
    else return $v;
}

function hashCode( $s )
{
    $h = 0;
    $len = strlen($s);
    for($i = 0; $i < $len; $i++)
    {
        $h = overflow32(31 * $h + ord($s[$i]));
    }

    return $h;
}

(edit: corrected %v typo)

Answer 2

There is no such method available in php. So you will have to implement the correct method. Wikipedia gives the algorithm used by Java.lang.hashCode which is used by strings I think, so here is a quick php version of it:

<?php
function getStringHashCode($string){
  $hash = 0;
  $stringLength = strlen($string);
  for($i = 0; $i < $stringLength; $i++){
    $hash = 31 * $hash + $string[$i];
  }
  return $hash;
}