Getting Started with PHP - Detailed Explanation of Basic Knowledge_PHP Tutorial

- Custom variable
         a. No need to indicate the data type
          b.Add '$'
                c. Begins with an underscore or letter
                                                                                                                                                                      Use meaningful words
-Congruent
        a.===
b. Determine the size and type
-Array
​​​​Create array method
a.array("key"=>"value")
          b.array[]=value;
           c.explode(separator,string);
Commonly used functions
a.count //Count the number of array items
            b.is_array //Determine whether it is an array
                                                            Traversing the array
Foreach($arr as $key=>$value)
​​​​​Description: Pointer jump, automatic loop, assignment in sequence
-Flow control character
a. break                     break n                                                                                                                                                                                                                                                  B. Continue // End this cycle
c. return exit e. The difference between return and exit: See picture
Picture: Figure 2-1.JPG



3. Function

-date("Y-m-d G:i:s")

a.Y represents the complete year represented by 4 digits

b.m The month represented by the number, with leading zeros

c.d The day of the month, a 2-digit number with leading zeros
d.G Hour, 24-hour format, no leading zeros
e. i Number of minutes with leading zeros
                      f. s                                                                                                                                                                                    seconds with leading zeros
Note: If the time you display is different from the time displayed on the computer, that is, there is a difference of 8 hours, you can change it in php.ini
Date.timezone = "PRC" //PRC represents the People's Republic of China
-time() //Returns the current Unix timestamp, which is a string of numbers
Example: $nextWeek=time()+(7*24*60*60);//7 days, 24 hours, 60 minutes, 60 seconds
echo $nextWeek."
";
echo 'now: '.date("Y-m-d")."n";
echo 'Next Week: '.date("Y-m-d",$nextWeek);

date (format character, timestamp)
1. Output the given timestamp in the given format
​ 2. If the timestamp is omitted, such as before, it is regarded as the current time

－Custom function

a.Format: function function name(){}
b. Use names related to functions

Function_exists //Judgement function
is_array //Judge array
－Naming convention
a. Use good names (required, the rest are for reference only)
b. Function words start with uppercase and lowercase letters
c. Capitalize constants
D. Variable lowercase Reminder: PHP is case sensitive

4.mysql
-Mysql (small relational database management system)
a.Small size
b. Fast
c. Low cost
d.Open source
MYSQL uses port 3306 by default
－Storage engine (type of storage table data)
a.MyISAM: higher insertion and query speed, but does not support transactions; default.
b.InnoDB: supports transactions
-phpMyAdmin (Access Mysql via Web)
－Type explanation
Precision: The total number of decimal digits stored in exponential data.
Length: refers to the number of bytes used to store data
int
1.Integer type
2. Accuracy 10
3. Value range (-2147483648~2147483648)
4.Length 4
Note:
int(n)
1. Specify the display width of the integer value
2. When the actual width is less than the specified column width, fill the width from the left
3.Do not change the length or the numerical range
 
Character type
char/varchar(n) //n represents length
When the character data values ​​in the columns have the same length, use char. When the lengths are different, use varchar to save storage space
－Basic sql statements
a.SELECT field FROM table WHERE condition
b.INSERT INTO table (field) VALUES (value)
c.UPDATE table SET update content WHERE condition
d.DELETE FROM table WHERE condition
          More practice is the key
​​After the query statement:
1.Group: group by
​ ​ 2. Sort:order by ASC/DESC
​ ​ 3.Limit:limit O,N
For limit, O is the offset, which starts from 0 like the array, and N is the number
For example: limit 1,5 is equivalent to 5 records starting from the second one
                                                                      5.php operates mysql
－Basic steps:
mysql_connect("hostname","username","password") //Connect to MYSQL
mysql_select_db("database_name"); //Open the database
Mysql_query($sql); //Execute sql statement
          mysql_fetch_array($result) //Value

mysql_query：

​​​ 1.When sql=select, a resource identifier is returned if the execution is successful, and FALSE
is returned if the execution error occurs.                                                                                                                                                   Note: The successful query does not mean that there will be results, it only means that the statement is correct
​ ​ 2. When sql=insert/update, TRUE is returned if the execution is successful, and FALSE
is returned if the execution error occurs.

mysql_fetch_array()

​ ​ 1. Obtain a row in the result set of query(sql) and save it to the array
​ ​ 2. Calling them in sequence will return the next row in the result set
3. You can index by field name
－Chinese encoding
​ ​ ​ Avoid garbled characters:
​ ​ 1. When establishing a database, select the corresponding character set. Nationally applicable: GBK/gb2312; Worldwide common: UTF-8 (recommended).
​ ​ 2. When connecting to mysql, add the connection character set "set names GBK";
Note: If you set names UTF8, then you should set the page encoding to UTF-8
                                                

代码如下	复制代码
///////////////封装Php连接Mysql函数////////////////         function PHPConnectMysql($hostname,$username,$password,$database,$charaset){              mysql_connect($hostname,$username,$password);              mysql_select_db($database);              mysql_query("set names $charaset");         }

Summary: Accumulate more and functionalize specific functions for reuse

http://www.bkjia.com/PHPjc/629247.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/629247.htmlTechArticle-Custom variable a. No need to indicate the data type b. Add '$' c. Start with an underscore or letter d. Use meaningful words - congruent a.=== b. Determine size and type - array creation array method a....