Many times, you will want your users to submit some data to your server. Similar to HTML Form WML also provide a mechanism to submit user data to web server.
To submit data to the server in WML, you need the <go>...</go> along with <postfield/> tags. The <postfield/> tag should be enclosed in the <go>...</go> tag pair.
To submit data to a server, we collect all the set WML variables and use <postfield> elements to send them to the server. The <go>...</go> elements are used to set posting method to either POST or GET and to specify a server side script to handle uploaded data.
In previous chapters we have explained various ways of taking inputs form the users. These input elements sets WML variables to the entered values. We also know how to take values from WML variables. So now following example shows how to submit three fields name, age and sex to the server.
<?xml version="1.0"?> <!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.2//EN" "http://www.wapforum.org/DTD/wml12.dtd"> <wml> <card id="card1" title="WML Form"> <p> Name: <input name="name" size="12"/> Sex : <select name="sex"> <option value="male">Male</option> <option value="female">Female</option> </select> Age : <input name="age" size="12" format="*N"/> <anchor> <go method="get" href="process.php"> <postfield name="name" value="$(name)"/> <postfield name="age" value="$(age)"/> <postfield name="sex" value="$(sex)"/> </go> Submit Data </anchor> </p> </card> </wml>
When you download above code on your WAP device, it will provide you option to enter three fields name, age and sex and one link Submit Data. You will enter three fields and then finally you will select Submit Data link to send entered data to the server.
The method attribute of the <go> tag specifies which HTTP method should be used to send the form data.
If the HTTP POST method is used, the form data to be sent will be placed in the message body of the request. If the HTTP GET method is used, the form data to be sent will be appended to the URL. Since a URL can only contain a limited number of characters, the GET method has the disadvantage that there is a size limit for the data to be sent. If the user data contains non-ASCII characters, you should make use of the POST method to avoid encoding problems.
There is one major difference between HTML and WML. In HTML, the name attribute of the <input> and <select> tags is used to specify the name of the parameter to be sent, while in WML the name attribute of the <postfield> tag is used to do the same thing. In WML, the name attribute of <input> and <select> is used to specify the name of the variable for storing the form data.
Next chapter will teach you how to handle uploaded data at server end.