PHP form learning: The use and difference of $_GET and $_POST variables

In the previous article, I brought you "PHP form learning: How to verify the email and URL in the form?"", which introduces in detail the knowledge about how to verify emails and URLs in forms in PHP. In this article, we take a look at the $_GET variables and $_POST variables in PHP. I hope everyone has to help!

In the previous article we have learned how to validate the required data and how to validate the email and URL in the form through regular expressions. Among them are the shadows of$_GETvariables and$_POSTvariables. Next, let’s take a look at$_GETvariables and$_POSTKnowledge related to the use of variables.

PHP $_GET Variables

We have learned about it before when we were studying# The ##$_GETvariable is used to collect values from the form withmethod="get". Information sent from a form with the GET method is visible to everyone (displayed in the browser's address bar), and there are limits on the amount of information sent. In fact, it can also be viewed as an array of variables passed to the current script through URL parameters.

When using $_GET variables, all variable names and values will be displayed in the URL. So this method should not be used when sending passwords or other sensitive information. However, because the variables appear in the URL, you can bookmark the page. In some cases this is useful.

Next let’s take a look at an example:

    
  
 名字: 
 性别：男 女
 年龄: 
  
  

The content submitted to demo.php is:

"; echo "你的性别是：" .$_GET['sex']."
"; echo "你的年龄是：".$_GET['age']; ?>

Output result:

We found that the values we filled in the form are all displayed in the Url column. So when do we use method="get"?

When using

method="get"in an HTML form, all variable names and values will be displayed in the URL. So you should not use this method when sending passwords or other sensitive information! However, because the variables appear in the URL, you can bookmark the page. In some cases this is useful.

It should be noted that the HTTP GET method is not suitable for large variable values. Its value cannot exceed 2000 characters.

$_POSTVariables

In the above example we Having talked about the

$_GETvariable, let’s take a look at the$_POSTvariable. The predefined$_POSTvariable is used to collect data frommethod= The value in the form of "post".

The information sent from the form with the POST method is not visible to anyone and will not be displayed in the browser's address bar like the

$_GETvariable, and is not visible to anyone. There is also no limit to the amount of information. However, by default, the maximum amount of information sent by the POST method is 8 MB, which can be changed by settingpost_max_sizein thephp.inifile.

Next let’s take a look at an example:

    
  
 名字: 
 性别：男 女
 年龄: 
  
  

The content submitted to demo.php is:

"; echo "你的性别是：" .$_POST['sex']."
"; echo "你的年龄是：".$_POST['age']; ?>

Output result:

We see that the information we submitted using POST is not displayed in the Url column, so POST is safer than GET. Let's summarize the differences between $_GET and $_POST. The difference between

##$_GETand$_POST

get

is to obtain data from the server, andpostis to transmit data to the server.get adds the parameter data queue to the URL pointed to by the ACTION attribute of the submitted form. The value corresponds to each field in the form and can be seen in the URL. Post uses the HTTP post mechanism to place each field in the form and its content in the HTML HEADER and transmit it to the URL address pointed to by the ACTION attribute. Users cannot see this process.

For the get method, the server side uses Request.QueryString to obtain the value of the variable. For the post method, the server side uses Request.Form to obtain the submitted data.

The amount of data transferred by get is small and cannot be larger than 2KB. The amount of data transmitted by post is relatively large and is generally unrestricted by default. But in theory, the maximum amount is 80KB in IIS4 and 100KB in IIS5.

Get security is very low, post security is high. But the execution efficiency is better than the Post method.

The differences between the two are organized into a table. The table is as follows:

##$_GET $_POST Display in url There will be a limit on the number of characters that will be displayed in the URL will not be displayed in the URL The amount of data submitted Generally a small amount of data less than 2k PHP can submit a large amount of 8M data by default ##In terms of security Submission principle Flexibility Common usage Through the difference we can conclude:

Unsafe	More secure
The submitted data is isolated	Submit the data as a whole
Very flexible, you can transfer data with a page jump	Not flexible, you must have the participation of a form
More commonly used	Less compared with $_GET

The get method is less secure than the Post method. If confidential information is included, it is recommended to use the Post data submission method;
is working When querying data, it is recommended to use the Get method; when adding, modifying or deleting data, it is recommended to use the Post method;
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