PHP programming is often easy to remember, PHP programming knowledge _ PHP Tutorial

PHP programming is often easy to remember, and PHP programming knowledge. PHP programming is often easy to remember, and PHP programming is often easy to remember. differences between echo and print: echo and print functions are basically the same (output) in PHP, but PHP programming is often confusing and PHP programming knowledge.

PHP is often easy to remember.

1. differences between echo and print

The echo and print functions in PHP are basically the same (output), but there are still slight differences between the two. No return value after echo output, but print has a return value. if the execution fails, flase is returned. Therefore, it can be used as a common function. for example, after the following code is executed, the value of $ r is 1.

$ R = print "Hello World ";

This means that print is available in some complex expressions, but echo is not. However, because the echo statement does not require any value to be returned, the running efficiency of the echo statement in the code is slightly faster than that of the print statement.

2. Differences Between include and require

The include () and require () functions are basically the same (include), but there are also some differences in usage. include () is a conditional include function, while require () it is an unconditional include function. For example, in the following code, if the variable $ a is true, it will contain the file a. php:

If ($ ){

Include ("a. php ");

}

The require () is different from include (). No matter what the value of $ a is, the following code will include file a. php into the file:

If ($ ){

Require ("a. php ");

}

For error handling, use the include statement. If an include error occurs, the program skips the include statement. Although the error message is displayed, the program continues to execute! But requre will give you a fatal error.

Of course, we can also understand the literal meaning of 7 points: requre is a very tough request and requirement.

3. require_once () and include_once () statements

Because of the long Image, simple require_once () and include_once () statements correspond to the require () and include () statements respectively. The require_once () and include_once () statements are mainly used to avoid repeated function or variable definition errors when you need to include multiple files.

4. differences between NULL strings ('') and NULL

PHP empty strings and NULL are both stored with 0 values, but their types are not the same. you can try echo gettype (''); and echo gettype (NULL ); you will find that the printed values are string and NULL, and of course there are also 0 which are easy to confuse. you can try echo gettype (0); print the type, the type of 0 is integer (integer). It can be seen that the string (''), NULL, and 0 are" equivalent "but not equal to the type.

5. differences between isset and empty

Literally, we can understand that empty is used to determine whether a variable is "null", while isset is used to determine whether a variable has been set. However, when the value of a variable is 0, empty considers the variable to be null, that is, it is equivalent to no setting. For example, when we detect the $ id variable, when $ id = 0, empty and isset are used to check whether the variable $ id has been configured. both of them return different values: empty considers that there is no configuration, and isset can get the value of $ id. See the following example:

$ Id = 0;

Empty ($ id )? Print "I am empty": print "I am $ id."; // result: I am empty

! Isset ($ id )? Print "I am empty": print "I am $ id."; // result: I am 0

6. Differences Between = (wait) and = (constant)

Let's review the difference between the fourth NULL string ("") and NULL. let's look at an example:

''= NULL;

''= NULL;

After running, you will find that the first is true, and the second is false! It can be seen that = only compares whether the values are equal, while = compares not only the values, but also the types and stricter.

7. difference between self: And this->

When accessing the member variables or methods in the PHP class, if the referenced variables or methods are declared as const (defining constants) or static (declaring static), the operator must be used:: if the referenced variable or method is not declared as const or static, the operator-> must be used.

In addition, if you access const or static variables or methods from the inside of the class, you must use self-referenced. Otherwise, if the internal access from the class is not a const or static variable or method, then you must use the self-referenced $ this.

8. differences between strstr () and strpos ()

Stristr () is case insensitive strstr () is case sensitive

The function is used to locate the first occurrence of a string in another string.

If successful, the rest of the string is returned (from the matching point ). If this string is not found, false is returned.

Stripos () is case insensitive strpos () is case sensitive

The function returns the position where the string first appears in another string.

If this string is not found, false is returned.

Tests show that strpos () is more efficient than strstr ()

9. HTTP_HOST and SERVER_NAME in PHP

Similarities:

When the following three conditions are met, the two will output the same information.

1. the server is port 80.

2. set ServerName correctly in apache conf.

3. HTTP/1.1 Protocol specification

Differences:

1. general situation:

_ SERVER ["HTTP_HOST"] under the HTTP/1.1 protocol specification, information is output according to the client's HTTP request.

_ SERVER ["SERVER_NAME"] by default, the ServerName value in the configuration file httpd. conf of apache is directly output.

2. when the server is not port 80:

_ SERVER ["HTTP_HOST"] outputs the port number, for example, mimiz.cn: 8080.

_ SERVER ["SERVER_NAME"] directly outputs the ServerName value

Therefore, it can be understood as: HTTP_HOST = SERVER_NAME: SERVER_PORT

3. when the ServerName in the configuration file httpd. conf is inconsistent with the domain name of the HTTP/1.0 request:

Httpd. conf is configured as follows:

ServerName pprar.com

ServerAlias http://www.pprar.com

Client Access domain name http://www.pprar.com

_ SERVER ["HTTP_HOST"] output http://www.pprar.com

_ SERVER ["SERVER_NAME"] output pprar.com

Therefore, in actual programs, _ SERVER ["HTTP_HOST"] should be used as much as possible, which is relatively safe and reliable.

For Port ING and intranet access, it is better to use "$ _ SERVER ['http _ X_FORWARDED_HOST.

PHP programming is easy to get started? For anyone who knows nothing about programming, how can I get started quickly to build a website?

It is not difficult for people with basic knowledge (for example, many people in the University have studied C) to use PHP.
PHP was initially developed with the aim of rapid development of a bunch of frameworks like Java
But you have never been familiar with advanced programming languages.
The difficulty is that after all, front-end languages such as html css are very different from advanced languages.
If you have the conditions, we recommend that you find friends around you to give you some basic programming ideas.
Basic knowledge about variables, loops, arrays, objects, functions, and so on
Buy a PHP entry or download a copy online. thanks for the simple code.
I feel that the basic knowledge is almost the same. Next, let's look at some standard source code to see how others write the code on the technical forum.
Then you can write your own website.

More advanced development is what will happen in the future. What are the objects? what are the design patterns? what are the frameworks?
You don't have to worry about the start of further development.

A good job can be found in php programming.

You can't do that. you need to use the php tag or directly process it in the php code. here is an example:

$ Result = mysql_query ("SELECT * FROM treename WHERE treeID = 1"); // The SQL syntax is incorrect.
$ Path = trim ($ result [1]);
$ Name = trim ($ result [2]);
$ Ext = trim ($ result [3]);
$ PicSrc = ""; // This is a bit redundant for you. just do the following:
$ PicSrc = $ picSrc. $ path. $ name. $ ext;
Echo "";
?>
</Td>
Second:

$ Result = mysql_query ("SELECT * FROM treename WHERE treeID = 1"); // The SQL syntax is incorrect.
$ Path = trim ($ result [1]);
$ Name = trim ($ result [2]);
$ Ext = trim ($ result [3]);
$ PicSrc = ""; // This is a bit redundant for you. just do the following:
$ PicSrc = $ picSrc. $ path. $ name. $ ext;
?>
"Width =" 500 ">
</Td>
I hope it will give you some valuable results !!

 

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