312 Part II . PHP and MySQL Basic Form Submission to a Database Submitting data to a database via an HTML form is straightforward if the form and formhandler are two separate pages. Listing 17-1, newsletter_signup.html, is a simple form with only one input field. Listing 17-1: A simple form (newsletter_signup.html)

Building Forms from Queries Form handling is one of PHP s very best features. The combination of HTML to construct a data-input form, PHP to handle the data, and a database server to store the data lies at the heart of all kinds of supremely useful Web tasks. HTML Forms You already know most of what you need to make good forms to be handled by PHP and a database. There are a few PHP-specific points to brush up on: . Always, always, always use a NAME for every data entry element (INPUT, SELECT, TEXTAREA, and so on). These NAME attributes will become PHP variable names you will not be able to access your values if you do not use a NAME attribute for each one. If your WYSIWYG editor doesn t allow you to do this, you ll need to remember to add these NAME attributes by hand. . A form field NAME does not need to be the same as the corresponding database field name, but it s often a good idea. . You can (and usually should) specify a VALUE rather than let HTML send the default value. Consider substituting a numerical value for a text value if possible, because the database is much slower at matching strings than integers. . The VALUE can be set to data you wish to display in the form. . Remember that you can pass hidden variables from form to form (or page) using the HIDDEN data entry elements. This practice may have negative security implications, but it s often no worse than storing the data in a cookie. . Remember that you can pass multiple variables in an array but you need to inform the user that this is a possibility. See Chapter 7 for more information on how to format an HTML form for use with PHP. Cross- Reference 1C H A7P7T E R . . . . In This Chapter Understanding HTML forms Submitting data via forms Self-submitting forms Editing data with an HTML form . . . .
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Chapter 16 . Displaying Queries in Tables 309 The only tricky thing in creating these sample tables is setting up the relational structure. We want each city row to have an appropriate countryID, which should be equal to the actual ID of the appropriate row from the country table. However, these countryIDs are automatically assigned in sequence by MySQL and are not under our control. How can we know the right countryID to assign? The answer is in the incredibly handy function mysql_insert_id(), which recovers the ID associated with the last INSERT query made via the given database connection. We insert the new country, recover the ID of the newly created row, and then use that ID in our city insertion queries. Summary Database interaction is one of the areas where PHP really shines. One very common use for database-enabled Web code is simply to display database contents attractively. One approach to this kind of display is to map the contents of database tables, or SELECT statements, to corresponding HTML table elements. When the mapping is simple enough, you can employ reusable functions that take arbitrary table names, or SELECT statements, and display them as a grid. When you need a more complicated combination of information from relational tables, you probably need a specialpurpose function, but certain tricks recur there as well. One such trick is to craft a SQL statement that returns all the information you need, in the order you want, and selectively print only the nonredundant portions. Near the end of this chapter, we saw a quick example of populating a set of database tables using INSERT statements. Aside from that, all the techniques in this chapter were read-only and do not modify the contents of databases at all. In Chapter 17, we ll see how you can get a more intimate connection to your database by combining SQL queries with HTML forms. . . .
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308 Part II . PHP and MySQL Listing 16-5 (continued) } function populate_cities_db($dbh) { /* drop tables if they exist — permits function to be tried more than once */ mysql_query( DROP TABLE city , $dbh); mysql_query( DROP TABLE country , $dbh); /* create the tables */ mysql_query( CREATE TABLE country (ID int not null auto_increment primary key, continent varchar(50), countryname varchar(50)) , $dbh) OR die(mysql_error()); mysql_query( create table city (ID int not null auto_increment primary key, countryID int not null, cityname varchar(50)) , $dbh) OR die(mysql_error()); /* store data in the tables */ add_new_country($dbh, Africa , Kenya , array( Nairobi , Mombasa , Meru )); add_new_country($dbh, South America , Brazil , array( Rio de Janeiro , Sao Paulo , Salvador , Belo Horizonte )); add_new_country($dbh, North America , USA , array( Chicago , New York , Houston , Miami )); add_new_country($dbh, North America , Canada , array( Montreal , Windsor , Winnipeg )); print( Sample database created
); } ?> You should be able to use this code to recreate the sample database on your development machine, assuming that you have PHP and MySQL configured, and an appropriately located file called phpbook-vars.inc containing username, password, and database-name strings. Just as in the display examples, this code sends off query strings (with embedded variables), but this time the queries are INSERT statements, which create new table rows. For the most part, the data inserted is just string data passed in to the function, although we chose to pass in an arbitrary number of cities per country by using an array.
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Chapter 16 . Displaying Queries in Tables 307 This code is somewhat tricky although it goes through the result rows in order, and everything it prints is grabbed from the current row, it prints countries only when their values have changed. (Continents are still printed redundantly.) The change in a country is detected by monitoring the ID field of the country row. A country change is also a signal to print out the HTML necessary to close off the preceding table row and start a new one. Finally, the code must handle printing the HTML necessary to start the first row and end the last one. Creating the Sample Tables Now we will show you the PHP/MySQL code we actually used to create the sample tables. (Such data might more normally be created by interacting only with MySQL, but we decided to respect our book s title by doing it from PHP.) The code (shown in Listing 16-5) is a specialpurpose, one-time hack, not a model of style, but it has useful examples of using the SQL INSERT statement. Listing 16-5: Creating the sample tables If you are in need for cheap and reliable webhost to host your website, we recommend http web server services.

306 Part II . PHP and MySQL Listing 16-4 (continued) print(