PHP Data type

PHP uses two types of data:

1, the number: including integral type, floating points.

Decimal: If you see 15 o'clock, it means (1*10+5) or 1510

Contains (0 ... 9) 10 digits

Octal: If you see 15 o'clock, it means (1*8+5) or 158 or 1310

Contains (0 ... 7) Eight digits

Hexadecimal: If you see 15 o'clock, it means (1*16+5) or 1516 or 2110

Contains (0 ... 9,A,B,C,D,E,F) 16 digits

2, Text: That is, as a processing unit of a string of characters.

2.1. Single quote string

Enclose the text you want to use in single quotes.

such as: ' I am siron. '

？ : If I am going to write this, the book is highly enjoyable. How do you write that?

2.2, double quote string

Use double quotes to enclose the text you want to use, but it's more complicated. You can use variable substitution in double quotes.

such as: "I am Siron."

？ : If I want to write Tom said, "Gifts are great." How do you write that?

Note: There are two problems ahead, is not simple to use single, double quotes can be resolved?

No, this will cause errors!!!

We have to mention the escape character "\": the function of the character immediately following will be ignored.

So, the 2.1 question can be written like this: ' This\ ' s book is highly enjoyable. '

2.2 of the questions can be written like this: "Tom said,\" Gifts are great.\ ""

Let's look at a larger difference between a single quote string and a double quote string:

You can add a special escape sequence in a double quote string

The escape sequence list is as follows:

Escape sequence	Describe
\ n	Line Wrap
\ r	Enter
\ t	Tabs
\$	Dollar sign
\0nnn	Any 18 in number
\xnn	Any number of hexadecimal digits
\\	Backslash character

Note: PHP uses "$" to define variables, so when you write "$", you use the escape character.

2.3, inverted quote character

PHP runs system commands with an inverted quote string