Learning outline:
1.php Seven types of variables
The distinction between 2.isset and empty two functions
3. Type test
4. Automatic conversion of type
5. Type cast
Attention:
1. The method invoked in the object is called by the variable-> method name. $user 1 = new per (); $user 1->say ();
2. Change the encoding of the page:
Header ("CONTENT-TYPE:TEXT/HTML;CHARSET=GBK");
3.header header information cannot have output
1.php Eight types of variables
Integral type
Floating-point type
Character type
Boolean type
The above four types are scalar types
Array
Object
Both of these types are composite types
Resources
Null type
Both of these types are special types
Integral type
$a = 10;
Floating-point type
$a = 10.3;
Character type
$a = "Hello world";
String links with. To link
Boolean type
$a =true;
Boolean types are generally calculated by comparison, > < >= <= = =!= = =!==
When you output a Boolean type with echo Print_r, True becomes 1,false and becomes empty
$a =true;
Var_dump ($a);
Array
Definition: When assigning multiple values to a variable
";
Print_r ($arr);
echo "
";?>
The value of the array:
Add to array:
Object type
Objects are made up of two parts: Features and functions, attributes, and methods
Say ();
? >
Resources
Null type
$a =null;
Based on the database link resources, action table:
id:{$row [' id ']} ';
echo "name:{$row [' Name ']}
";
}
? >
The distinction between 2.isset and empty two functions
Whether the isset variable exists and does not exist:
1) No definition
2) NULL
Empty whether the variable is empty or empty:
1) # 0
2) ""
3) "0"
4) False
5) Array ()
6) NULL
7) No definition
3. Type test
Var_dump ();
1. Integral type is_int ();
2. Floating-point type is_float ();
Database connection: -->$conn = mysql_connect ("localhost", "root", "1234");
Var_dump (Is_resource ($conn));
?>
4. Automatic conversion of type
1. Integral type-> string
2. String-> integral type
$num = "1243alj";
strings are automatically converted to integral type
echo $num +1;
3. Other types of-> Boolean types
1) # 0
2) ""
3) "0"
4) False
5) Array ()
6) NULL
7) No definition
All of the above Boolean types are fake
5. Type cast
(int) $num integral type
(float) $num floating-point type
(string) $num string
(BOOL) $num Boolean
To delete a variable using:
$num = "User";
Unset ($num);
Var_dump (Isset ($num));
Single double quotation marks for strings:
1. There are no variables in the string, use single quotes
2. If you have a variable, use double quotes (single quotes can be used, but you need to use. To link)
Definition of constants:
Like a variable, but once defined, it can't be modified.
Define ("HOST", "localhost");
Define ("USER", "root");
Define ("Pass", "123");
Define ("dbname", "Test");
For example, the database configuration file, this time to use constants, and can not be modified after.
Output of constants:
Echo HOST;
Constants cannot be placed in double quotes
echo "My host is". HOST;
Operator
