PHP Quick Tips, Quick Tips_PHP Tutorial

PHP quick fix, quick fix

A brief introduction to the syntax of PHP

1. Embedding method:

Similar to ASP's <%, PHP can be . Of course, you can also specify it yourself.

2. Referenced documents :

There are two ways to reference files: require and include.
The usage method of require is as require("MyRequireFile.php");. This function is usually placed at the front of the PHP program. Before the PHP program is executed, it will first read in the file specified by require and make it a part of the PHP program web page. Commonly used functions can also be introduced into web pages in this way.

include is used like include("MyIncludeFile.php"); . This function is generally placed in the processing part of flow control. The PHP program webpage only reads the include file when it reads it. In this way, the process of program execution can be simplified.

3. Annotation method :

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4. Variable type :

Two questions arise here. First, PHP variables start with $, and second, PHP statements end with ;. ASP programmers may not adapt to this. These two omissions are where most errors in the program lie.

5. Operation symbols :

Mathematical operations: Symbol Meaning
+ Addition
- Subtraction operation
* Multiplication
/ Division operation
% Take the remainder
++ Accumulate
-- Decreasing

String operations:

There is only one operator symbol, which is the English period. It can concatenate strings into new merged strings. Similar to &

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Two questions also arise here. First, the output statement in PHP is echo. Second, it is similar to <%=variable%> in ASP. In PHP, it can also be .

Logical operations:

Symbol Meaning
> Greater than
<= less than or equal to
>= greater than or equal to
== equals
!= is not equal to
&& And (And)
and And (And)
|| Or (Or)
or or (Or)
xor exclusive or (Xor)
! Not (Not)

Learning purpose: Master the process control of php

1. If..else loop has three structures

The first is to use only the if condition and treat it as a simple judgment. Interpreted as "what to do if something happens". The syntax is as follows:

if (expr) { statement }

The expr is the condition for judgment, usually using logical operation symbols as the condition for judgment. The statement is the execution part of the program that meets the conditions. If the program has only one line, the curly brackets {} can be omitted.

Example: This example omits the curly braces.

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Special attention here is that == is used to determine whether they are equal, not =. ASP programmers may often make this mistake, = is assignment.

Example: The execution part of this example has three lines, and the curly brackets cannot be omitted.

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The second type is that in addition to if, an else condition is added, which can be interpreted as "what to do if something happens, otherwise how to solve it." The syntax is as follows

if (expr) { statement1 } else { statement2 } Example: Modify the above example into a more complete processing. Since there is only one line of instructions for executing else, there is no need to add braces.

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The third type is the recursive if..else loop, which is usually used in various decision-making judgments. It combines several if..else statements for processing.

Look directly at the example below

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The above example only uses a two-level if..else loop to compare two variables a and b. When actually using this kind of recursive if..else loop, please use it with caution, because too many levels of loops can easily cause problems with the design logic, or missing braces, etc., can cause inexplicable problems in the program.

2. There is only one type of for loop , with no changes. Its syntax is as follows

for (expr1; expr2; expr3) { statement }

where expr1 is the initial value of the condition. expr2 is the condition for judgment, and logical operators are usually used as the condition for judgment. expr3 is the part to be executed after statement is executed. It is used to change the conditions for the next loop judgment, such as adding one, etc. The statement is the execution part of the program that meets the conditions. If the program has only one line, the curly brackets {} can be omitted.

The following example is written using a for loop.

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3. Switch loop usually handles compound conditional judgments. Each sub-condition is part of the case instruction. In practice, if many similar if instructions are used, it can be synthesized into a switch loop.

The syntax is as follows

switch (expr) { case expr1: statement1; break; case expr2: statement2; break; default: statementN; break; }

The expr condition is usually a variable name. The exprN after case usually represents the variable value. After the colon is the part to be executed that meets the condition. Be sure to use break to break out of the loop.

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What needs to be noted here is break; don’t omit it, default, omission is okay.

Obviously, using the if loop in the above example is very troublesome. Of course, when designing, you should put the conditions with the greatest probability of occurrence at the front and the conditions with the least occurrence at the end, which can increase the execution efficiency of the program. In the above example, since the probability of occurrence is the same every day, there is no need to pay attention to the order of the conditions.

Learning purpose: Learn to build a database

In ASP, if it is an ACCESS database, you can directly open ACCESS to edit the MDB file. If it is a SQL SERVER, you can open the Enterprise Manager to edit the SQL SERVER database. However, in PHP, the command line editing of MY SQL may It's very troublesome for beginners. It doesn't matter. You can download PHPMYADMIN and install it. You can rely on it to build and edit the database in the future.

Let’s talk about its use.
After entering phpmyadmin, we first need to create a database. Select Chinese Simplified Language (*) here, then create a new database on the left, fill in the database name here, and click Create.

Then select the created database in the drop-down menu on the left.

Create a new table in database shop:
Name:
Number of fields:

with the table name and the approximate number of fields you think (it doesn’t matter if there are not enough or more, you can add them later or default them), and press Execute.
Then you can start creating the table.
The first column is the name of the field; the second column selects the field type:
The ones we commonly use are the following:
1) VARCHAR, text type
2) INT, integer type
3) FLOAT, floating point type
4) DATE, date type
5) You may ask, where is the automatically added ID? Just select the INT type and select auto_increment in the following extras.

After creating the table, you can see the table you created on the left. After clicking, you can:
1) Press the structure on the right: View the modified table structure
2) Press Browse on the right: View the data in the table
3) Press SQL on the right: Run SQL statement
4) Press insert on the right: insert a row of records
5) Press Clear on the right: delete all records in the table
6) Press delete on the right: delete table

Another very important function is import and export. When we have completed the program and database locally, we need to have a local mirror on the server. If it is ASP ACCESS, it is simple. Just upload the MDB file directly. Yes, if it is SQL SERVER, you can also connect to the remote server for import. Then you can export all SQL statements in MY SQL, go to PHPMYADMIN on the remote server, create the database, press SQL, and paste all the SQL statements generated by this level that you just copied.

Learning purpose: Learn to connect to the database

PHP is simply a function library. The rich functions make some parts of PHP quite simple. It is recommended that you download a PHP function manual so that you can always use it.

I will briefly talk about connecting to the MYSQL database.

1. mysql_connect

Open a MySQL server connection.
Syntax: int mysql_connect(string [hostname] [:port], string [username], string [password]); Return value: integer

This function establishes a connection to the MySQL server. All parameters can be omitted. When this function is used without any parameters, the default value of the hostname parameter is localhost, the default value of the username parameter is the owner of the PHP execution process, and the password parameter is an empty string (that is, there is no password). A colon and port number can be added after the parameter hostname to indicate which port to use to connect to MySQL. Of course, when using a database, using mysql_close() early to close the connection can save resources.

2. mysql_select_db

Select a database.
Syntax: int mysql_select_db(string database_name, int [link_identifier]); Return value: integer

This function selects the database in the MySQL server for subsequent data query processing (query). Returns true on success, false on failure.

The simplest example is:
$conn=mysql_connect ("127.0.0.1", "", "");
mysql_select_db("shop");
Connect to the MY SQL database and open the SHOP database. In practical applications, error judgment should be strengthened.

Learning purpose: Learn to read data

Let’s look at two functions first:
1. mysql_query
Send a query string. Syntax: int mysql_query(string query, int [link_identifier]); Return value: integer

This function sends the query string for MySQL to perform related processing or execution. If the link_identifier parameter is not specified, the program will automatically look for the most recently opened ID. When the query string is Update, Insert and Delete, the returned value may be true or false; when the query string is Select, a new ID value is returned. When false is returned, it does not mean that the execution is successful but there is no return value, but There is an error in the query string.

2. mysql_fetch_object returns class data . Syntax: object mysql_fetch_object(int result, int [result_typ]); Return value: Class

This function is used to split the query result result into a class variable. If result has no data, a false value is returned.

Look at a simple example:

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Of course, there is a username field in the user table, which is similar to

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Of course, we need to connect to the database first. Generally, we require_once('conn.php'); and conn.php contains the code to connect to the database mentioned last time.

Learning purpose: Learn to add, delete and modify data

mysql_query($exec);
This statement alone can perform all operations. The difference is the $exec sql statement

Add: $exec="insert into tablename (item1,item2) values ​​('".$_POST['item1']."',".$_POST['item1'].")";

Delete: $exec="delete from tablename where...";

Modify: $exec="update tablename set item1='".$_POST['item1']."' where ...";

At this point, we have to talk about form and php variable transfer. If an
If the form is submitted by POST, then you can use $_POST['item1'] to get the variable value when processing the form file. Similarly, if it is submitted by GET, it is $_GET['item1']

Isn’t it very simple? But usually $exec will have problems, because your SQL statement may be very long, and you will miss the .connection character, or ' to surround the character field.
We can comment out the mysql_query($exec); statement and replace it with echo $exec; to output $exec to check for correctness. If you still can't detect any errors in $exec, you can copy this sql statement and execute it in phpmyadmin to see its error message. It should also be noted that we should not use some sensitive strings as field names, otherwise problems may occur, such as date and so on. It is sometimes good for you to follow a little rule when naming variables and fields. Beginners should not ignore its importance.

Learning purpose: Learn how to use SESSION

SESSION has many functions, the most commonly used one is the transfer of variables between pages within the site. At the beginning of the page we need session_start(); to open SESSION;
Then you can use the SESSION variable. For example, to assign a value: $_SESSION['item']="item1"; to get the value, $item1=$ _SESSION['item'];, it's very simple. Here we may use some functions, for example, to determine whether a SESSION variable is empty, you can write: empty($ _SESSION['inum']) returns true or false.

Let’s take a look at a login procedure based on what we said earlier to determine whether the username and password are correct.
The login form is like this: login.php

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处理文件是这样

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conn.php是这样：

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由于 $_SESSION['adminname']=$username;我们可以这样写验证是否登陆语句的文件：checkadmin.asp

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学习目的：做一个分页显示

关键就是用到了SQL语句中的limit来限定显示的记录从几到几。我们需要一个记录当前页的变量$page，还需要总共的记录数$num

对于$page如果没有我们就让它=0，如果有<0就让它也=0，如果超过了总的页数就让他=总的页数。

这样可以得到记录总数
ceil($num/10))如果一页10记录的话，这个就是总的页数

所以可以这么写