Chú ý tuyên bố trở lại kêu gọi các chức năng điện, nhưng nó là trừ đi một từ biến $ số mũ mỗi khi nó được gọi là. Cuối cùng $ số mũ sẽ đánh số không và nếu tuyên bố sẽ không thực hiện. Tại thời điểm này là khi đệ quy kết thúc. Lấy một cái nhìn chuyên sâu tại các công trình này như thế nào. | 136 Chapter 7 Playing with Chess and Databases Open the database if it isn t there create it db OpenDatabase dbPath dbType if db db CreateDatabase dbPath dbType if db exit If you get here the database has opened successfully and you can do what you want with it. Looping through the Database Now that you know how to create and open a non-relational database it would be handy to know how to loop through the data in the database to display it. To loop through a database record set you need to start at the very first key. PHP provides you with dba_firstkey to get the first key of a specified database. string dba_firstkey int databaseHandle Once you retrieve the first key of the database you need to loop through each record until there are no more records. For this you will use a while loop because you won t know the count of elements in the record set. To get the value you use the dba_fetch function. string dba_fetch string key int databaseHandle The dba_fetch function will return a string of false if it was unable to get the data. Once you have retrieved the data you will need to unserialize the data just like you will have to serialize the data to put it into the database. string unserialize string someString After you have done this you can do what you want with the unserialized string. Then you need to retrieve the next key in order to move to the next record. Take a look at the following example to see how it all works together php dbPath dbType db3 db OpenDatabase dbPath dbType Inserting an Entry into Your Database 137 if db db CreateDatabase dbPath dbType if db exit Get the first record key dba_firstkey db Loop through the whole database while key false value dba_fetch key db entry unserialize value Do something with entry key dba_nextkey db dba_close db Note Remember to always close the database you re working with by using the dba_close function. Inserting an Entry into Your Database To insert an entry PHP provides you with the dba_insert .
