PHP lesson three basic data types for PHP
Learning outline:
1.php Seven types of variables
The distinction between 2.isset and empty two functions
3. Type testing
4. Automatic conversion of types
5. Type casting
Attention:
1. The method called in the object is invoked through 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
The above two 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 obtained by comparison operations, > < >= <= = = = = = = = = = = = =!==
When you output a Boolean type with echo Print_r, true turns into 1,false and becomes empty
$a =true;
Var_dump ($a);
Array
Definition: When assigning multiple values to a variable
";p Rint_r ($arr); echo"
";? >
The value of the array:
To add an array:
Object type
Objects consist of two parts: Features and functions, properties and methods
Say (); ? >
Resources
Null type
$a =null;
Based on the database Link resource, the action table:
id:{$row [' ID ']} "echo"name:{$row [' Name ']}
";}? >
The distinction between 2.isset and empty two functions
Isset whether the variable exists, does not exist:
1) No definition
2) NULL
Empty if the empty variable is null:
1) 0
2) ""
3) "0"
4) False
5) Array ()
6) NULL
7) No definition
3. Type testing
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 types
1. Integer-string
2. String-Integer
$num = "1243alj";
String auto-to-integer
echo $num +1;
3. Other types: Boolean type
1) 0
2) ""
3) "0"
4) False
5) Array ()
6) NULL
7) No definition
The above-mentioned Boolean types are all fake.
5. Type casting
(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 quotes for strings:
1. There is no variable in the string, just use single quotation marks
2. If there are variables, use double quotation marks (single quotation marks can also be used, but need to use. To link)
Definitions of constants:
Same as variables, but cannot be modified once defined
Define ("HOST", "localhost");
Define ("USER", "root");
Define ("PASS", "123");
Define ("DBNAME", "Test");
For example, the database configuration file, this time to use a constant, and can not be modified later.
Output of the constant:
Echo HOST;
Constants cannot be placed in double quotes
echo "My host is". HOST;
Operator
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