php内置函数分析之array_change_key_case()

PHP_FUNCTION(array_change_key_case)
{
    zval *array, *entry;
    zend_string *string_key;
    zend_string *new_key;
    zend_ulong num_key;
    zend_long change_to_upper=0;

    if (zend_parse_parameters(ZEND_NUM_ARGS(), "a|l", &array, &change_to_upper) == FAILURE) {
        return;
    }

    array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(array)));

    ZEND_HASH_FOREACH_KEY_VAL(Z_ARRVAL_P(array), num_key, string_key, entry) {
        if (!string_key) { // 数组键值为数字索引，将数组元素更新到return_value        
            entry = zend_hash_index_update(Z_ARRVAL_P(return_value), num_key, entry);
        } else { // 数组键值为字符串
            // 字符串键值大小写转换
            if (change_to_upper) {
                new_key = php_string_toupper(string_key);
            } else {
                new_key = php_string_tolower(string_key);
            }
            // 将数组元素更新到return_value
            entry = zend_hash_update(Z_ARRVAL_P(return_value), new_key, entry);
            // 释放zend_string, 如果引用数位0，则释放内存。
            zend_string_release(new_key);
        }
        // 增加引用
        zval_add_ref(entry);
    } ZEND_HASH_FOREACH_END();
}