Hash function for PHP associative arrays

Issue

I understand that PHP associative arrays are stored in a Hash Table.
What hashing function is used for the string ‘keys’ ?

Solution

From zend/hash.h:

/*
 * DJBX33A (Daniel J. Bernstein, Times 33 with Addition)
 *
 * This is Daniel J. Bernstein's popular `times 33' hash function as
 * posted by him years ago on comp.lang.c. It basically uses a function
 * like ``hash(i) = hash(i-1) * 33 + str[i]''. This is one of the best
 * known hash functions for strings. Because it is both computed very
 * fast and distributes very well.
 *
 [...]
 *                  -- Ralf S. Engelschall 
 */

static inline ulong zend_inline_hash_func(const char *arKey, uint nKeyLength)

Answered By – VolkerK

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