An introductory tutorial to PHP that is absolutely suitable for novices

An introductory tutorial on PHP that is absolutely suitable for novices

What do I need?

In this tutorial, we assume that your server already supports PHP and that all files have a .php3 extension. On most servers this is a missing extension for PHP files, you can check with your administrator. If your server supports PHP, this is enough. It's simple, create your PHP file and put it on your server, and the server will handle it smartly. This requires no compilation or installation of any additional tools. You can think of it this way: PHP files are regular HTML files with a new set of clever tags added.

Your first PHP code

The color of the above code is just to give you a visual help, making it easier for you to understand PHP tags and expressions different parts of the formula. Please note that unlike CGI programs, executable permissions are not required. You can think of a PHP file as an HTML file containing a set of special tags that can do any number of things you're interested in.

This program is very simple, you don't need to create a WEB page specifically for this. All it does is display: Hello World.

If you try this code and it outputs nothing, the problem may be that your server does not support PHP. Please ask your administrator to confirm.

The focus of the previous example is to introduce you to PHP tags. Use the "" tag. As shown in the example, you can freely enter and exit PHP mode in HTML files.

Some useful stuff

Let’s do something more meaningful. If we want to check what the user's browser is, we can check the user agent (User Agent) string sent by the browser to the WEB server. This information is stored in a variable named $HTTP_USER_AGNET. The value of this variable can be easily displayed by using the following statement:

<?php
 echo $HTTP_USER_AGENT;
?>

If the user is using Internet Explorer, the displayed result may be : Mozilla/4.0 (compatible; MSIE 4.0; Windows 98) In fact, the user's browser also delivers a lot of other content. You can get a complete list of these variables with the following code:

<?php
 phpinfo();
?>

Save this code into a file, say info.php3, and then upload it to your server and use your browser Open it and you'll see a lot of things that will surprise you. You can place multiple PHP statements within a set of PHP tags, or use a single block of code to do more. For example: If we want to check whether the browser is MSIE, we can use the following code:

<?php if (strstr($HTTP_USER_AGENT,"MSIE"))
{
　　echo "You are using Internet Explorer.<br>";
}
?>

Here we will introduce some new things. First is the "if" statement. If you are familiar with the basic syntax of C language, then you will easily understand this code. If you are not familiar with it, it is recommended to find some related books for reference. PHP retains the simple syntax of C and avoids the difficult-to-control string and memory processing in C language.

Second, we called a function: strstr(). strstr() is a built-in function in PHP, used to find another string in a string. In the example, we search for "MSIE" in the variable $HTTP_USER_AGENT. If the font string is found, then the function returns a true value, that is, TRUE , otherwise vice versa.

Let’s take a look at how to enter and exit PHP mode, even in the middle of a PHP code block:

<?php
if (strstr($HTTP_USER_AGENT,"MSIE")){
?>
<center><b>You are using Internet Explorer</b></center>
<?
}else{
?>
<center><b>You are not using Internet Explorer</b></center>
<?
}
?>

Use the method of jumping out of PHP mode to directly output HTML code instead of using echo Statement output results. It is very important to not destroy the logical integrity of the PHP code. The result displayed by running this code may be:

You are using Internet Explorer

Processing the form

Another PHP The power lies in processing forms in html files. You need to understand the basic concept that all HTML file form elements will automatically be sent to the target page with the same name. This seems a bit difficult to understand. Let's illustrate this through the following example:

<form action="action.php3" method="post">
Your Name: <input type=text name=name> 字串3
Your Age : <input type=text name=age>
<input type="submit">
</form>

This form only contains the necessary HTML tags and is not complete. When the user fills out this form and presses the "Submit" button, the file action.php3 is called. Suppose this file contains the following code:

Hi <?php echo $name;?>. You are <?php echo $age;?> years old.

The effect of its execution is obvious, because the variables $name and $age are automatically set by PHP.

Thank you all for reading, I hope you will benefit a lot.

This article is reproduced from: https://blog.csdn.net/ffghggf/article/details/86659891

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