PHP determines whether the form form is submitted Detailed explanation

phpDetermine whether the form is submitted

When we generally submit a form through submit, we will care about filling in a lot of information in the form. Whether the data is submitted to the background. Here you need to make a judgment. Using PHP code to determine whether the form data has been submitted generally takes the following form:

<?php
if(isset($_POST[&#39;submit&#39;])) { 
  echo " 数据被提交过来了";
} 
?>

Description: isset -- detects whether the variable is set. The return value is as follows of several forms.

If the variable does not exist, return FALSE

If the variable exists and its value is NULL, it also returns FALSE

If the variable exists and its value is not NULL, then TRUE is returned

When checking multiple variables at the same time, TRUE will be returned only when each single item meets the previous requirement, otherwise the result will be FALSE.

php form submission method GET and POST request

GET method puts the data and the requested URL address together, browse The results are placed in the cache area. Since GET is passed after the URL, the size of the data passed is limited.

The data sent by POST is stored separately in the package and does not follow the URL address, so a large amount of data is allowed to be sent, but the client will send a request to the server every time and will not be stored in the cache. within the area. You can use $_POST[] to receive POST data. In the URL, no data information will be displayed.

Let’s analyze the difference between the two submission methods:

1. GET is to obtain data from the server, and POST is to transmit data to the server. .
2. 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.
3. For GET method to submit form data, the server side uses $_GET['name'] to obtain the value of the variable. For POST method to submit form data, the server side uses $_POST['name'] to obtain the submitted data. Of course , both can obtain form data through $_REQUEST['name']. For submitting form data in REQUEST mode, the server uses $_REQUEST[‘name’] to obtain the value of the variable, but this method is rarely used.
4. The amount of data transmitted by GET is small and cannot be larger than 2KB. The amount of data transmitted by POST is large and is generally unrestricted by default. But in theory, it is generally believed that it cannot exceed 100KB.
5. GET security is very low, POST security is high.
6. The GET form value can be obtained through _GET; but the parameters set through the action URL cannot always be obtained,