Walk into php-data type and string syntax

PHP supports 8 types of raw data

Four types of scalar:

Boolean | Integer | Float (as Double) | String

Two kinds of composite types:

Array | Object

Two special types of

Resource | Null

Among them, the maximum value of the shaping depends on the machine, Php_int_max is the maximum value of the storage;

If you want to see the value and type of an expression, use the Var_dump () function to view

The GetType () function can be used to get the type of expression, and then to debug;

The Is_type () function can view a type:

Eg:is_int () | Is_string () | etc

Cast a variable to a type by using the Settype () function;

Integer overflow: If a number exceeds the range of int, it is interpreted and the result of the operation is returned to float;

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A string is expressed in 4:

(1) Single quotation mark

In single quotes, except ' and \, two characters need to be escaped, and any other backslash will be the backslash itself;

(2) Double quotation marks

Special characters can be resolved in double quotation marks

\ n line Break | \ r Enter | \ t Horizontal tab | \e ESCAPE | \f Page Change | \ \ Backslash | \$ USD | \ "Double quotation marks

(3) Heredoc structure: <<< lable

After the operator to provide an identifier, and then the number, followed by the string itself, and finally with the previously defined identifier as the end flag, the end of the reference identifier must be in the first column of the row.

eg

1 $str = <<<eoo2  HELLO3  Wold  4 eoo; 　　

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(4) Nowdoc structure:<<< ' lable '

The HEREDOC structure resembles a double-quote string, and Nowdoc resembles a single-quote string without parsing. Suitable for embedding PHP code or other interrupted text without having to transfer special characters within it. Unlike Heredoc, tokens need to be marked with single quotes.

(5) Variable resolution

When a string is defined in double quotation marks or heredoc, the variable is parsed.

When PHP encounters a $, it combines as many representations as possible to form a valid variable name. Therefore, you can use curly braces {} to define the bounds of the variable name.

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Array

Arrays are defined by array (), and the arrays in PHP are actually an ordered map that associates values to the keys.

5.4 can use [] instead of array ()

eg

　　$array Array　　("foo" = "bar");  $array = ["foo" = "Bar"];

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If more than one cell in the array definition uses the same key name, only the last one is used, and the previous is overwritten.

Key is optional. If not specified, PHP will automatically use the maximum integer key name previously used plus 1 as the new key name.

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Simple syntax for object:

1<?PHP2 classFoo3 {4     functionDo_doo ()5     {6     Echo"Doing foo";7     }8 }9 $bar=Newfoo;Ten $bar-Do_foo (); One?>

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Walk into php-data type and string syntax