The example HTML page above contains two input fields and a submit button. When the user fills in this form and click on the submit button, the form data is sent to the "welcome. The "welcome. Form Validation User input should be validated whenever possible. Client side validation is faster, and will reduce server load. However, any site that gets enough traffic to worry about server resources, may also need to worry about site security. You should always use server side validation if the form accesses a database.
A good way to validate a form on the server is to post the form to itself, instead of jumping to a different page. The user will then get the error messages on the same page as the form. This makes it easier to discover the error. Information sent from a form with the GET method is visible to everyone it will be displayed in the browser's address bar and it has limits on the amount of information to send max.
So this method should not be used when sending passwords or other sensitive information! However, because the variables are displayed in the URL, it is possible to bookmark the page. This can be useful in some cases. Information sent from a form with the POST method is invisible to others and has no limits on the amount of information to send.
However, because the variables are not displayed in the URL, it is not possible to bookmark the page. Syntax date format,timestamp. Specifies the format of the timestamp Optional. Specifies a timestamp. Default is the current date and time as a timestamp.
A timestamp is the number of seconds since January 1, at GMT. This is also known as the Unix Timestamp. It uses letters to represent date and time formats. Here are some of the letters that can be used: d - The day of the month m - The current month, as a number Y - The current year in four digits An overview of all the letters that can be used in the format parameter, can be found in our PHP Date reference.
This parameter is optional. If you do not supply a timestamp, the current time will be used. In our next example we will use the mktime function to create a timestamp for tomorrow.
The mktime function returns the Unix timestamp for a specified date. Server Side Includes You can insert the content of a file into a PHP file before the server executes it, with the include or require function. The two functions are identical in every way, except how they handle errors. The include function generates a warning but the script will continue execution while the require function generates a fatal error and the script execution will stop after the error.
These two functions are used to create functions, headers, footers, or elements that can be reused on multiple pages. Page 30 of This means that you can create a standard header or menu file that you want all your web pages to include. When the header needs to be updated, you can only update this one include file, or when you add a new page to your site, you can simply change the menu file instead of updating the links on all web pages.
The include Function The include function takes all the text in a specified file and copies it into the file that uses the include function. Example 1 Assume that you have a standard header file, called "header.
Example 2 Now, let's assume we have a standard menu file that should be used on all pages include files usually have a ". Look at the "menu. The three files, "default. Here is the code in "default. And, of course, we would have to do the same thing for "about. By using include files, you simply have to update the text in the "menu.
The require Function The require function is identical to include , except that it handles errors differently. If you include a file with the include function and an error occurs, you might get an error message like the one below.
Notice that the echo statement is still executed! This is because a Warning does not stop the script execution. Now, let's run the same example with the require function. Error message: Warning: require wrongFile. The echo statement was not executed because the script execution stopped after the fatal error. It is recommended to use the require function instead of include , because scripts should not continue executing if files are missing or misnamed.
Starts at the beginning of the file Write only. Opens and clears the contents of file; or creates a new file if it doesn't exist Append. Preserves file content by writing to the end of the file Write only.
Creates a new file. Note: If the fopen function is unable to open the specified file, it returns 0 false. The feof function is useful for looping through data of unknown length. Note: You cannot read from files opened in w, a, and x mode!
Reading a File Line by Line The fgets function is used to read a single line from a file. Note: After a call to this function the file pointer has moved to the next line. Reading a File Character by Character The fgetc function is used to read a single character from a file. Note: After a call to this function the file pointer moves to the next character. Create an Upload-File Form To allow users to upload files from a form can be very useful.
For example, when viewed in a browser, there will be a browse-button next to the input field Note: Allowing users to upload files is a big security risk. Only permit trusted users to perform file uploads. For security reasons, you should add restrictions on what the user is allowed to upload. Restrictions on Upload In this script we add some restrictions to the file upload. The user may only upload. Saving the Uploaded File The examples above create a temporary copy of the uploaded files in the PHP temp folder on the server.
The temporary copied files disappears when the script ends. The script above checks if the file already exists, if it does not, it copies the file to the specified folder.
Note: This example saves the file to a new folder called "upload". What is a Cookie? A cookie is often used to identify a user. A cookie is a small file that the server embeds on the user's computer.
Each time the same computer requests a page with a browser, it will send the cookie too. With PHP, you can both create and retrieve cookie values. How to Create a Cookie? The setcookie function is used to set a cookie. Syntax setcookie name, value, expire, path, domain ;. In the example below, we will create a cookie named "user" and assign the value "Alex Porter" to it.
Note: The value of the cookie is automatically URLencoded when sending the cookie, and automatically decoded when received to prevent URLencoding, use setrawcookie instead. Example 2. You can also set the expiration time of the cookie in another way. It may be easier than using seconds. How to Retrieve a Cookie Value? How to Delete a Cookie? When deleting a cookie you should assure that the expiration date is in the past.
If your application deals with browsers that do not support cookies, you will have to use other methods to pass information from one page to another in your application. One method is to pass the data through forms forms and user input are described earlier in this tutorial.
The form below passes the user input to "welcome. Retrieve the values in the "welcome. Session variables hold information about one single user, and are available to all pages in one application. PHP Session Variables When you are working with an application, you open it, do some changes and then you close it. This is much like a Session. The computer knows who you are. It knows when you start the application and when you end. But on the internet there is one problem: the web server does not know who you are and what you do because the HTTP address doesn't maintain state.
A PHP session solves this problem by allowing you to store user information on the server for later use i. However, session information is temporary and will be deleted after the user has left the website. If you need a permanent storage you may want to store the data in a database. Before you can store user information in your PHP session, you must first start up the session. The code above will register the user's session with the server, allow you to start saving user information, and assign a UID for that user's session.
In the example below, we create a simple page-views counter. The isset function checks if the "views" variable has already been set. If "views" has been set, we can increment our counter. Description Required. Specifies the subject of the email. Note: This parameter cannot contain any newline characters Required.
Defines the message to be sent. Lines should not exceed 70 characters Optional. Specifies additional headers, like From, Cc, and Bcc. Specifies an additional parameter to the sendmail program. Note: For the mail functions to be available, PHP requires an installed and working email system.
The program to be used is defined by the configuration settings in the php. Read more in our PHP Mail reference. This is a simple email message. This is how the example above works: First, check if the email input field is filled out If it is not set like when the page is first visited ; output the HTML form If it is set after the form is filled out ; send the email from the form When submit is pressed after the form is filled out, the page reloads, sees that the email input is set, and sends the email Note: This is the simplest way to send e-mail, but it is not secure.
In the next chapter of this tutorial you can read more about vulnerabilities in e-mail scripts, and how to validate user input to make it more secure. Page 47 of The problem with the code above is that unauthorized users can insert data into the mail headers via the input form. What happens if the user adds the following text to the email input field in the form? The mail function puts the text above into the mail headers as usual, and now the header has an extra Cc:, Bcc:, and To: field.
When the user clicks the submit button, the e-mail will be sent to all of the addresses above! An error message with filename, line number and a message describing the error is sent to the browser. Page 50 of If your code lacks error checking code, your program may look very unprofessional and you may be open to security risks. This tutorial contains some of the most common error checking methods in PHP. We will show different error handling methods: Simple "die " statements Custom errors and error triggers Error reporting.
If the file does not exist you might get an error like this: Warning: fopen welcome. The code above is more efficient than the earlier code, because it uses a simple error handling mechanism to stop the script after the error. However, simply stopping the script is not always the right way to go. Let's take a look at alternative PHP functions for handling errors. Creating a Custom Error Handler Creating a custom error handler is quite simple. We simply create a special function that can be called when an error occurs in PHP.
This function must be able to handle a minimum of two parameters error level and error message but can accept up to five parameters optionally: file, line-number, and the error context :. Specifies the error report level for the user-defined error. Must be a value number. See table below for possible error report levels. Specifies the filename in which the error occurred Optional.
Specifies the line number in which the error occurred. Specifies an array containing every variable, and their values, in use when the error occurred. Error Report levels These error report levels are the different types of error the user-defined error handler can be used for: Page 52 of Description Non-fatal run-time errors.
The code above is a simple error handling function. When it is triggered, it gets the error level and an error message. It then outputs the error level and message and terminates the script. Now that we have created an error handling function we need to decide when it should be triggered. Page 53 of We are going to make the function above the default error handler for the duration of the script. It is possible to change the error handler to apply for only some errors, that way the script can handle different errors in different ways.
The output of the code above should be something like this: Error: [8] Undefined variable: test. Trigger an Error In a script where users can input data it is useful to trigger errors when an illegal input occurs. An error can be triggered anywhere you wish in a script, and by adding a second parameter, you can specify what error level is triggered.
Errors that can not be recovered from. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally. The output of the code above should be something like this: Error: [] Value must be 1 or below Ending Script. Now that we have learned to create our own errors and how to trigger them, lets take a look at error logging. Sending errors messages to yourself by e-mail can be a good way of getting notified of specific errors.
The output of the code above should be something like this: Error: [] Value must be 1 or below Webmaster has been notified. And the mail received from the code above looks like this: Error: [] Value must be 1 or below. This should not be used with all errors. Regular errors should be logged on the server using the default PHP logging system. PHP Exception Handling Exceptions are used to change the normal flow of a script if a specified error occurs.
Exception handling is used to change the normal flow of the code execution if a specified error exceptional condition occurs. This condition is called an exception. This is what normally happens when an exception is triggered: The current code state is saved The code execution will switch to a predefined custom exception handler function Depending on the situation, the handler may then resume the execution from the saved code state, terminate the script execution or continue the script from a different location in the code We will show different error handling methods: Basic use of Exceptions Creating a custom exception handler Multiple exceptions Page 57 of Note: Exceptions should only be used with error conditions, and should not be used to jump to another place in the code at a specified point.
Basic Use of Exceptions When an exception is thrown, the code following it will not be executed, and PHP will try to find the matching "catch" block.
If an exception is not caught, a fatal error will be issued with an "Uncaught Exception" message. Try, throw and catch To avoid the error from the example above, we need to create the proper code to handle an exception. Page 58 of Proper exception code should include: 1. Try - A function using an exception should be in a "try" block. If the exception does not trigger, the code will continue as normal.
However if the exception triggers, an exception is "thrown" 2. Throw - This is how you trigger an exception. Each "throw" must have at least one "catch" 3. Example explained: The code above throws an exception and catches it: 1. The checkNum function is created. It checks if a number is greater than 1. If it is, an exception is thrown Page 59 of The checkNum function is called in a "try" block 3.
The exception within the checkNum function is thrown 4. Creating a Custom Exception Class Creating a custom exception handler is quite simple. We simply create a special class with functions that can be called when an exception occurs in PHP.
The class must be an extension of the exception class. The custom exception class inherits the properties from PHP's exception class and you can add custom functions to it.
The new class is a copy of the old exception class with an addition of the errorMessage function. Since it is a copy of the old class, and it inherits the properties and methods from the old class, we can use the exception class methods like getLine and getFile and getMessage. Example explained: The code above throws an exception and catches it with a custom exception class: 1. The customException class is created as an extension of the old exception class. This way it inherits all methods and properties from the old exception class 2.
The errorMessage function is created. This function returns an error message if an e-mail address is invalid 3. The "try" block is executed and an exception is thrown since the email address is invalid 5. The "catch" block catches the exception and displays the error message. Multiple Exceptions It is possible for a script to use multiple exceptions to check for multiple conditions.
It is possible to use several if.. Example explained: The code above tests two conditions and throws an exception if any of the conditions are not met: 1. The "try" block is executed and an exception is not thrown on the first condition 5. The second condition triggers an exception since the e-mail contains the string "example" Page 62 of The "catch" block catches the exception and displays the correct error message If there was no customException catch, only the base exception catch, the exception would be handled there.
Re-throwing Exceptions Sometimes, when an exception is thrown, you may wish to handle it differently than the standard way.
It is possible to throw an exception a second time within a "catch" block. A script should hide system errors from users. System errors may be important for the coder, but is of no interest to the user. Example explained: The code above tests if the email-address contains the string "example" in it, if it does, the exception is re-thrown: 1.
The "try" block contains another "try" block to make it possible to rethrow the exception 5. The exception is triggered since the e-mail contains the string "example" 6. The "catch" block catches the exception and re-throws a "customException" 7.
The "customException" is caught and displays an error message If the exception is not caught in its current "try" block, it will search for a catch block on "higher levels". In the code above there was no "catch" block.
Instead, the top level exception handler triggered. This function should be used to catch uncaught exceptions. Code may be surrounded in a try block, to help catch potential exceptions Each try block or "throw" must have at least one corresponding catch block Multiple catch blocks can be used to catch different classes of exceptions Exceptions can be thrown or re-thrown in a catch block within a try block.
What is a PHP Filter? A PHP filter is used to validate and filter data coming from insecure sources. To test, validate and filter user input or custom data is an important part of any web application. The PHP filter extension is designed to make data filtering easier and quicker.
Why use a Filter? Almost all web applications depend on external input. Usually this comes from a user or another application like a web service. By using filters you can be sure your application gets the correct input type. Page 65 of You should always filter all external data! Input filtering is one of the most important application security issues. What is external data? CSS Text W3. CSS Round W3. CSS Padding W3.
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