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AJAX Basics

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GET and POST

6:21 with Dave McFarland

Learn about the two most common methods for sending requests to a web server. What is the difference between the two and when to use GET, when to use POST?

Key Points

There are two common methods for sending HTTP requests:

  • GET. Used for most requests. Browser uses the GET method whenever it requests a new web page, CSS file, image, and so on. Use GET when you want to "get" something from the server.
  • POST. Used frequently with web forms to send data to store in a database. Use POST when sending data that will store, delete or update information from a database.

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    Ajax isn't that hard. 0:00
    We've already looked at the basic steps required 0:01
    to set up and send an Ajax request. 0:04
    First you create the XMLHttpRequest object, then you define 0:07
    a callback function, you open the request, and then you send it. 0:11
    As I mentioned in the last video opening a request requires specifying the method 0:16
    you'll use to send the request and the URL you'll send the request to. 0:21
    The two most common methods are GET and POST. 0:25
    Here's an easy way to think about which method you should use. 0:29
    Use GET when you're only interested in 0:32
    receiving or getting information from a server. 0:34
    Such as the result of a database search or retrieving a set of tweets. 0:37
    Use post when sending data that's going to be saved 0:43
    like an email address for an email newsletter sign-up form. 0:45
    Or a vote for a Reddit post. 0:49
    You use the GET method all the time when you 0:52
    open a web browser and type in a web address. 0:54
    The web browser uses a get to request a webpage. 0:57
    The GET method is meant to get a resource, like 1:00
    a webpage, image, or other file from a web server. 1:03
    In other words, all that's required for a get request is a url. 1:07
    But with AJAX, we frequently want more than just a static file of text or HTML. 1:12
    We're after dynamic, that is, changing information. 1:17
    Like the latest tweets from your friends, the results of 1:20
    a web search, or information on an employee in a business. 1:23
    For a server site program to send 1:27
    you customized information, like the map of your 1:29
    current location or photos from your flickr account, 1:32
    you need to send the server some information. 1:35
    You can do this by adding data to the url sent to the server. 1:38
    You may have seen urls that look something like this. 1:43
    The part after the question mark is called a query string. 1:47
    A query string appears at the end of a URL and provides a way to 1:51
    send additional information that a web server can 1:54
    use to control the output of its response. 1:57
    Commonly, the data in a query string is used to search a database 2:01
    of information and return just a single record or a small subset of information. 2:05
    In this case, the file employees.php 2:11
    is programmed using the PHP programming language. 2:14
    In other words, it's not a regular old HTML file, it's a program 2:18
    that does something and it requires information so it knows what to do. 2:22
    Its purpose might be to retrieve information on employees at the company. 2:26
    This information is often sent in a query string. 2:30
    A query string is made up of one or more name value pairs. 2:34
    In this example the query string contains one name value pair. 2:38
    lastName equals Jones. 2:42
    lastName is the name or property. 2:45
    The equal sign assigns a value to that property. 2:47
    Jones is the value here. 2:51
    Query strings can hold multiple name value pairs. 2:53
    Simply add an ampersand, followed by another 2:56
    name, an equal sign and another value. 2:59
    There are some requirements for query strings. 3:01
    Most importantly, you can't just use any symbol you want in a query string. 3:05
    Some characters like the ampersand, equal, space, and 3:10
    quote marks have special meaning in a URL. 3:13
    So if you send information that includes 3:17
    those special characters you need to encode them. 3:19
    That is, translate them into a set of symbols that 3:22
    are safe and don't conflict with their URL specific version. 3:25
    For example, ampersand is represented by %26. 3:29
    A space is converted to a plus. 3:33
    And a plus is converted to %2B. 3:37
    There 3:40
    are lots of online tools that demonstrate what URL encoded strings look like. 3:42
    The site URL Encode and Decode online is one of them. 3:47
    For example, let me type in a string with spaces, quotes, and an ampersand. 3:51
    [BLANK_AUDIO] 3:55
    Now, when I click the URL encode button, you can see how it's translated. 4:01
    You can also use this tool to decode a URL encoded string. 4:07
    Don't worry about memorizing these codes. 4:11
    As you'll learn later, JavaScript and jQuery both 4:13
    include functions that do this conversion for you. 4:16
    The GET method is a simple way to send data to a web server. 4:19
    However, there are some down sides to it. 4:22
    First, all of the data is sent in the URL, which means that if you need 4:25
    to send sensitive information, like a social security 4:29
    number, a password or your personal telephone number. 4:32
    It will appear in the computer's browser history 4:35
    and show up in the web server's log files. 4:38
    This isn't the most secure solution. 4:41
    Second, there's only so much information you can put into a URL. 4:43
    For example, Internet Explorer can only handle URLs that are 2083 characters long. 4:47
    When you need to send lots of information, 4:54
    like a blog post, the get method isn't good. 4:56
    That's why http offers another method called POST. 4:59
    The POST method sends data differently than get. 5:03
    Whereas get puts all its information in the url, the post method sends 5:06
    data separate from the url, in what's called the body of the request. 5:11
    For example, say you had a sign up 5:15
    form on your site with username and password fields. 5:17
    Using get to submit that form, you'd see 5:21
    the username and password in the URL like this. 5:23
    However, using post, the URL to the sign up script has no extra information. 5:28
    The actual form data is sent separate from the URL. 5:34
    Not only is this more secure, it also let's 5:37
    you send a lot more information to the server. 5:40
    The post method does require special encoding, just like get requests. 5:42
    In addition, you need to set up a special header for the request. 5:47
    That's an instruction, sent to the server, telling 5:52
    it what kind of data it should expect. 5:54
    In many cases, you can use either get or post, but 5:58
    the basic rule of thumb is that if you're requesting information, 6:00
    like search results, new HTML to add to a page, 6:04
    photos from a photo service and so on, use get. 6:07
    On the other hand, use post if you're 6:11
    sending information that's to be stored in a database, 6:13
    if the data is sensitive, like a password, or 6:16
    if you're sending lots of information from a form. 6:19

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