Detailed explanation of integer data types in PHP

Data types supported in php

　There are mainly 8 data types supported in php. and a form of the pseudotype in 3. The 8 data types are divided into the following three categories. The first is our scalar type. The scalar type can only store a single data. The second category is our composite type. The third is the special type. For these three categories, let’s first look at them one by one.

　In the first category, scalar types are divided into the following four subcategories. The first one is our integer type. As for the integer type, you can use int to represent the integer type, or integer to represent the integer type. The second is our floating point type, which can be represented by float or double double precision floating point or real real number. The third is that our Boolean type can be represented by bool or boolean. The fourth is that our string type can represent a string through string.

　 Data type - integer

So first of all, let’s look at it one by one. Let’s look at our integer type first. In fact, we have been writing integer type. We have written 123 to us. My age is 12. This is all an integer. type, or -123, which all represent integer types, so what we write are all in decimal, and we can also write those numerical values. We can write octal numbers and hexadecimal, which all represent integer types. Then we also need to know a storage range of the integer type.

　The storage range of integers, signed: -2.1 billion, just remember a rough range, between positive 2.1 billion; -200 million ~ 2.1 billion.

What about the unsigned one? That is 0 to 4.2 billion; 0 to 4.2 billion; such a form. Then there is one more thing you need to know. Since there is a storage range, then we now say that the addition of two integers must equal an integer? Not necessarily, because exceeding the storage range of integers will produce a phenomenon called overflow. What? Let’s take our example. If you take a one-liter cup and you want to put ten liters of water in it, the hole will not be able to hold it and someone will leak out.

Since you want to hold ten liters of water, you can only use a larger container to hold it. Then you will use our floating point type. As for the floating point type, you first need to know its storage The range is larger than the integer type. Don't worry, let's write a few integers first and take a look.

　 Let’s declare an integer variable. First write $int=1; echo $int; you will see a 1, then write another $int=-12; the same negative number also represents our integer , echo $int; then write another octal number $int=0x123; then echo $int; you will see if it is the value you want. $int=0xffff;This represents a hexadecimal number.

　　

　header('content-type:text/html;charset=utf-8');

　　 //Declare an integer type

　 $int=1;

　 echo $int,'
';

　 $int=-12;

　 echo $int,'
';

　 $int=0x123;//Octal

　 echo $int,'
';

　 $int=0xffff;//Ten Hexadecimal

　 echo $int,'
';

　 Run this example.

Then first, it goes without saying that 1, -12, then we will look at it later.

When you write an octal number, 291 is displayed. Then remember that in reality, this octal system is converted into decimal system, and the displayed decimal system is always a decimal system. Similarly, you can see that the hexadecimal 0xffff is converted into decimal in the form of our 65535.

　The values ​​you see now all represent integers, but we can’t say how we can get the type of a variable just by seeing it. We can write the detailed information of the variable by printing it through a function here, a common function.

　The first one: var_dump(); Use this function to directly print the detailed information of the variable to the browser. Then you have to tell me which variable you want to print. You can print one at a time or multiple at a time, in this form .

　 Then let’s use this var_dump(); var_dump($int); let’s declare an $int=0;

Then you will see an integer 0 on the browser; This prints an integer and its details.

First of all, you can see that this is the type of the variable. The 0 in the brackets is the value of the variable. You need to know this. Then when you see the int, it proves that it is an integer, no problem.

　　

　header('content-type:text/html;charset=utf-8');

　　 //Declare an integer type

　 $int=1;

　 echo $int,'
';

　 $int=-12;

　 echo $int,'
';

　 $int=0x123;//Octal

　 echo $int,'
';

　 $int=0xffff;//Ten Hexadecimal

　 Echo $int,'
';

　 //How to get the type of variable

　 $int=0;

var_dump($int);//int(0)