PHP and MySQL by Example- P9

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Nội dung Text: PHP and MySQL by Example- P9

Even though there is only one image, when the user clicks somewhere on it, the accompanying form will be sent to the server with the location of where the user clicked his or her mouse on the picture; that is, the pixel coordinates represented as two variables in the PHP script, image_name_x and image_name_y (image_name is the name assigned to the name attribute of the image input type; that is, toy_x and toy_y). The actual variable names sent by the browser contain a period rather than an underscore (toy.x and toy.y) but, as we discussed earlier in this chapter, PHP will automatically convert a period (or space) to an underscore because periods (and spaces) are not legal characters in PHP variable names. In the following example, after the user clicks on any of the check boxes, he or she will then click on the picture of the pizza man. This causes the form to be submitted with an array of values selected from the check boxes, as well as the x/y coordinates of where the user clicked on the image button. Example 10.14. Code View: (The HTML File) Image Button 1 Pick your pizza: 2 Tomato and Cheese Salami Pineapple and Ham Canadian bacon Plain Cheese Press the pizza man to order! 3 ------------------------------------------------------------------ (The PHP Script) Finding Pixel Coordinates Pizza Choices
print ""; 5 foreach ( $_POST['topping'] as $value ){ print "$value"; } print ""; } print "The pixel coordinates of the image are: "; 6 $coord1 = $_POST['pizzas_x']; $coord2 = $_POST['pizzas_y']; print "$coord1, $coord2"; ?> Explanation 1 The form, shown in Figure 10.23, is being submitted to a PHP script using the POST method. 2 The form consists of a set of check boxes that will be passed to PHP as an array called "topping". 3 Here is where we create the image button to be used to submit the form. It is given a name of "pizzas" and the image src is "Pizza_chef.jpg" located in the current working directory or folder. When the user clicks on this picture, the form will be submitted. 4 If the user has posted the form, there will be a value in the $_POST array, the expression will test true, and the block will be entered. 5 For each of the toppings in the $_POST array, the values will be printed. See Figure 10.24. 6 The x/y coordinates represent the place in the image (pixel position) where the user clicked his or her mouse button. To check whether or not the form was submitted, you can test if these variables are not empty with the empty() function: if ( ! empty($coord1 ) Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.23. PHP output after processing multiple selections. Figure 10.24. Using an image to submit a form. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.25. After the form input has been processed, the user’s choices are listed as well as the pixel positions of the image button (the pizza man). 10.3.10. Self-Processing HTML Forms Rather than creating a separate HTML document to display a form and another PHP script to process the user input, you might want to combine the HTML document containing the form and the PHP script that processess it all into one script. This is done by assigning the $_SERVER['PHP_SELF'] array to the action attribute of the HTML tag as shown in Example 10.15. When the user submits the form information by pressing the submit button, the action attribute of the form references the URL of the same page that displayed the form. Because both the HTML form data and the PHP processing code are in the same script, you will need a conditional check in your PHP program to see if the form has been submitted. For example, you can check to see if a field has a value, the submit button has been clicked, or check the request method used. The following examples demonstrate how this is done. Checking If the Form Was Submitted Example 10.15 shows the script that checks whether a form was submitted. Example 10.15. Code View: First HTML Form 5
6 Please enter your name: Please enter your phone: Explanation 1 The PHP isset() function checks to see if the form has been submitted using the POST method. If it has, the program continues at line 2; if not, then program control goes to line 4, and the form will be displayed in the browser. 2 Because the form has already been submitted, the values that were entered into the fields can be displayed as variables. See Figure 10.27. 3 The superglobal $_SERVER['SELF'] array contains information about the path where this script is found starting at the document root of the server, not the root of the file system. 4 If the form has not been submitted, the script jumps into this block where we switch from PHP into the HTML mode to produce the form. See Figure 10.26. 5 The action attribute is assigned the address of the current script. The program temporarily switches back into PHP mode to get the path of the script from the $_SERVER['PHP_SELF'] variable. When the user presses the submit button, this same script will be reexecuted, this time to process the form data. 6 The user is presented with two text boxes, as shown in Figure 10.26. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.26. The script displays the form. Figure 10.27. The same script processes the form. 10.3.11. Using Hidden Fields If your Web page contains multiple forms, you can use hidden fields to help identify what form needs to be processed by giving each form its own name. By checking the existence and value of the hidden field, you can determine which form should be displayed and when it should be processed. You can also use hidden fields to include information that can be used when processing the form but is not something that you do not care to display, such as the date the form was created, your name, and so on. Example 10.16. Code View: Hidden Fields Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
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Explanation 1 The isset() function will check to see if the variable $_POST['feedback1'] has been set and if it contains the value assigned to the hidden field. If both conditions are true, then the form has already been displayed on the browser and sent back to this PHP script. Because the page has already been displayed and submitted, it is now time to process the form. The user-‐defined function, process_form(), is called. 2 If the test on line 1 fails, then the form has not been previously displayed. The user-‐defined function, display_form(), is called. 3 The function display_form() will be responsible for creating the form and displaying it in the browser. 4 This is the start of a here-‐doc used to print out the HTML form and interpolate any variables. Remember that when in a here-‐doc you are essentially in a quoted block of text. Adding additional quotes to the array elements will produce an error. 5 The $_SERVER['PHP_SELF'] is a reference to the current script. When the user presses the submit button, the action is specified to call this same script again. 6 The hidden field is set as an input type of the tag. Although it will not be visible when the form is displayed, its name and value will be sent to the PHP script, along with the name and value of the radio button selected by the user. 7 The hidden field is assigned the month and year when this form was created. No one needs to see this information, except maybe you if you are trying to keep track of the development of this page. 8 The user-‐defined terminator, EOF, for marking the end of the here-‐doc, cannot have spaces on either side; that is, it must be butted up against the left margin, immediately followed by a newline. 9 After the user has filled out the form, this function processes the input received from the server. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.28. Using hidden fields to determine when to process this form. Output from Example 10.16. Figure 10.29. Output based on what radio button was selected in Figure 10.28. 10.3.12. Redirecting the User What if your Web site has moved to a new location? Now when your users go to the old site, you want to redirect them to the new one. What if you want to send the user to a different page depending on some condition: Is the user logged on? Did he or she forget his or her password? What language does he or she speak? Is it a holiday? The Location Header Redirecting a user to another page is easy and quick with PHP. It is done with the built-in header() function to modify the HTTP response header sent by the server. The location header can be changed by sending an HTTP Location followed by the URL of the new location. The header information must be sent to the browser before any HTML and text; therefore, it is important that the header() function is executed first. The following example would be wrong because the program is trying to send the echo output before the header information. The warning is displayed in Figure 10.30. (See “Buffering and HTTP Headers” on page 689 if you want to move the header after other output lines.) Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.30. The header must be sent first. Example 10.17. Explanation After being redirected, a user’s Back button will take the user where he or she was before the redirection page, not back to the redirection page itself. Using the Correct URI for Redirection The Location can be assigned the absolute URI of the redirection page such as the scheme, host name, and absolute path. Then the server will return a “redirect” header to the browser to retrieve the specified page directly. Location: http://marakana.com/company.html If you want to reference another file on your own server, you can output a partial URL, such as the following: Location: /tutorial/PHP/index.html You can make use of PHP’s $_SERVER array variables to specify an absoute path. For example, the $_SERVER['HTTP_HOST'], the $_SERVER['PHP_SELF'], and the path of the the current script returned by the dirname() function can be concatenated together to make an absolute URL from a relative one. The following PHP code defines a header described in the PHP manual:
Example 10.18. Code View: (The HTML File) Redirecting the User 1 Select a search engine 2 Google Yahoo! Lycos PHP Index 3 ------------------------------------------------------------------ (The PHP Script) Explanation 1 The form’s action attribute is assigned the path to the PHP script that will handle the redirect once the form is submitted. The HTML form is shown in Figure 10.31. 2 The HTML select menu will give the user options to choose from. 3 As soon as the user clicks the submit button, the form information will be sent to the server and handled by the PHP script listed in the form’s action attribute. 4 If the user did not select anything, the value of $_POST[new_url] will be empty, and the script will exit. 5 If the user selected one of the search engines in the menu (Figure 10.32), he or she will be directed to that Web site with the PHP header() function. The value of $_POST[new_url] is the address of the selected Web site; for example, http://www.lycos.com. Once the user is redirected, he or she can use the brower’s Back button to go back to the page where the selection was made. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
button to go back to the page where the selection was made. Figure 10.31. The HTML Web page before viewing the menu and selecting an option. Figure 10.32. The user selects “PHP Index” from the drop-down menu and presses “Get the Web Page!” to redirect to that site. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
10.3.13. Uploading Files In an HTML form, users can upload files from a browser to a Web server. The files might be text files, binary files (such as images or compressed files), spreadsheets, or other data (see http://www.faqs.org/rfcs/rfc1867.html). Being able to upload files is also useful if the information is easier to handle from a separate file, such as a registration form or a résumé. To upload files, you will need to create a form using the "file" type. Attributes for the Tag and the file Type To upload files the tag has three attributes: • The action attribute of the tag specifies the PHP script that will process the form. • The enctype attribute determines how the form data is encoded by the browser. The default value is application/x-www-form-urlencoded, which is the default for almost any kind of form data. However, if you are going to upload files then you must specify that the data is of enctype multi- part/form-data. The browser encodes form data differently for application/x-www-form- urlencoded and multipart/form-data. • The method attribute should be "POST". Example 10.19. (Sample File Upload Form Values) 1 4 5 Choose a file to upload: In addition to the three attributes, the form’s input type is "file"; for example:
PHP’s $_FILES Array When the file is sent to the server, PHP stores all the uploaded file information in the $_FILES superglobal array (see Table 10.3), a two-dimensional array that contains the name of the file input device as the first index and one of the attributes of the file type as the second index. Table 10.3. The $_FILES Superglobal Array Array Description $_FILES['userfile']['name'] The original name of the file on the client machine. $_FILES['userfile']['type'] The MIME type of the file, if the browser provided this information. An example would be "image/gif". $_FILES['userfile']['size'] The size, in bytes, of the uploaded file. $_FILES['userfile']['tmp_name'] The temporary filename of the file in which the uploaded file was stored on the server. $_FILES['userfile']['error'] The error code associated with this file upload. ['error'] was added in PHP 4.2.0. Example 10.20. Code View: (The HTML File) Uploading Files Uploading Files 1 Type the name of the file to upload: 5 -------------------------------------------------- (The PHP Script--upload_file.php) Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Explanation 1 The form starts here and is displayed in Figure 10.33. 2 The attribute to the form type is enctype and assigned "multipart/form- data". This encoding type is used to send data from files. 3 The action attribute specifies the PHP script that will process the uploaded files. 4 Uploaded files must be sent via the POST method. 5 The input device is of type "file" and will be assigned the name "user_file". The name is how the uploaded file will be identified in the PHP file, not the real name of the file. See Figure 10.35. 6 The $_FILES['user_file']['tmp_name'] array holds the name of the temporary file that PHP gave to the uploaded file. The fopen() function will open that file for reading and return a filehandle that allows access to the file. (See “The fopen() Function” on page 448.) Figure 10.33. The file upload form from Example 10.20 in the browser. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Figure 10.34. The user selects the Browse button in the form. Figure 10.35. The user then selects a file. Moving the Uploaded File PHP provides the move_uploaded_file() function to move an uploaded file to a new location. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
Format bool move_uploaded_file ( string filename, string destination ) This function checks to ensure that the file designated by filename is a valid upload file (meaning that it was uploaded using the POST method). If the file is valid, it will be moved to the filename given as a destination. If the filename is not a valid upload file, then no action will occur, and move_uploaded_file() function will return FALSE with a warning. Example 10.21. Code View: (The HTML Form) Uploading Pictures Uploading Files Browse and select the picture you want to upload: 2 --------------------------------------------------------------- (The PHP Script) File Uploads Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.
10.3.14. Sticky Forms A sticky form is a form that remembers the values you typed in the input fields. A typical example is when you fill out a form to purchase some products or fill out a registration form and you left out a field or typed the credit card information wrong. When you submit the order, the page comes back with the form and tells you what you did wrong and asks you to resubmit the order. If the order form is long and contains lots of boxes, how many times will you resubmit it, if you have to start all over again? With a sticky form, the input data can be saved so that when the form is redisplayed, the data is still there. The following example checks if the user left any fields empty and if he or she did, redisplays the form with an error showing what fields need to filled. The fields that had data in them still contain the data. (For a complete discussion on form validation, see Chapter 12, “Regular Expressions and Pattern Matching.”) Example 10.22. Code View: Empty Fields Validating Input
13 What is your phone number? Explanation 1 The $errors array is initialized. It will be used to build a string error message. 2 If the isset() function returns true, the user has already submitted the form and program control will go to line 3. 3 The user-‐defined function, validate_input(), is called. 4 If the PHP count() function finds that the $errors array is not empty, the display_form() function is called and the same form is displayed again with the error messages displayed in red. See Figures 10.38 and 10.39. 5 If there are no errors, then the form will be processed. We do not do any real processing here, but if we did, this is where the code would go. 6 If line 1 is false (i.e., the form has not yet been displayed), the form will be shown in the browser for the first time. 7 This is a user-‐defined function that will determine whether or not the user filled in the required fields. 8 The global keyword makes this array available within the function. 9 If the user did not fill the "name" field, the $errors array will be assigned a string of text as its value. The key 'name' is the name of the text box. 10 This function displays the form, as displayed in Figure 10.37. Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark.