Optimize array_unique()

In SORT_STRING mode, instead of sorting the array, build a hash of
seen elements.

Author: nikic

ext/standard/array.c

@@ -4477,14 +4477,51 @@ PHP_FUNCTION(array_unique)
 		Z_PARAM_LONG(sort_type)
 	ZEND_PARSE_PARAMETERS_END();
 
-	cmp = php_get_data_compare_func(sort_type, 0);
-
-
 	if (Z_ARRVAL_P(array)->nNumOfElements <= 1) {	/* nothing to do */
 		ZVAL_COPY(return_value, array);
 		return;
 	}
 
+	if (sort_type == PHP_SORT_STRING) {
+		HashTable seen;
+		zend_long num_key;
+		zend_string *str_key;
+		zval *val;
+
+		zend_hash_init(&seen, zend_hash_num_elements(Z_ARRVAL_P(array)), NULL, NULL, 0);
+		array_init(return_value);
+
+		ZEND_HASH_FOREACH_KEY_VAL_IND(Z_ARRVAL_P(array), num_key, str_key, val) {
+			zval *retval;
+			if (Z_TYPE_P(val) == IS_STRING) {
+				retval = zend_hash_add_empty_element(&seen, Z_STR_P(val));
+			} else {
+				zend_string *str_val = zval_get_string(val);
+				retval = zend_hash_add_empty_element(&seen, str_val);
+				zend_string_release(str_val);
+			}
+
+			if (retval) {
+				/* First occurrence of the value */
+				if (UNEXPECTED(Z_ISREF_P(val) && Z_REFCOUNT_P(val) == 1)) {
+					ZVAL_DEREF(val);
+				}
+				Z_TRY_ADDREF_P(val);
+
+				if (str_key) {
+					zend_hash_add_new(Z_ARRVAL_P(return_value), str_key, val);
+				} else {
+					zend_hash_index_add_new(Z_ARRVAL_P(return_value), num_key, val);
+				}
+			}
+		} ZEND_HASH_FOREACH_END();
+
+		zend_hash_destroy(&seen);
+		return;
+	}
+
+	cmp = php_get_data_compare_func(sort_type, 0);
+
 	RETVAL_ARR(zend_array_dup(Z_ARRVAL_P(array)));
 
 	/* create and sort array with pointers to the target_hash buckets */

ext/standard/tests/array/array_unique_variation8.phpt

@@ -35,22 +35,6 @@ Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
 
 Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
 
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
-Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
-
 Notice: Array to string conversion in %sarray_unique_variation8.php on line %d
 array(1) {
   [0]=>