What are the data types in php? Summary of php data types

This article brings you what are the data types of PHP? The summary of PHP data types has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

1. Introduction to data types

1. PHP is a weak type checking language. The data type is determined by the context of the program, that is, the specific type is determined by the stored data
2 , Three types of data types: scalar data type, composite data type and special data type
3. Scalar data type

• boolean Boolean type

• integer Integer type

• ##float/double floating point type

• string String string

4. Composite data type

• array array

• object object

5. Special data type

• resource Resource

• NULL Empty

2. Scalar data type

Boolean 1. Save a logical true or false

2. The following situations can also be regarded as false:

  Boolean value false, integer value 0, floating point value 0.0, empty string and string "0",
Array without member variables, object without unit, NULL

<?php 
//布尔型数据
$a = true;$b = false;
//var_dump()函数可以返回表达式的类型和值
var_dump($a);      //结果为  bool(true)echo "<br>";
var_dump($b);      //结果为  bool(false)
 ?>

Integer type (integer) 1. It can only contain integers, and symbols can be used to represent positive and negative numbers

2. Unsigned integers are not supported in PHP

//整型数据
$a = +3;$b = -5;
var_dump($a);      //结果为  int(3) 
echo "<br>";
var_dump($b);      //结果为  int(-5)
echo "<br>";
echo $a+$b;        //结果为  -2
echo "<br>";

Floating point type (float/double)

1. Floating point type is used to store decimals Number is an approximate numerical value

2. Scientific notation: 10.1e10

//浮点型数据
$a = 1.56;$b = 1.5e3;
var_dump($a);      //结果为  float(1.56) 
echo "<br>";
var_dump($b);      //结果为  float(1500)

String type (string) 1. Single quotation mark
  Variables appearing in single quotes will be output as they are, and the PHP engine will not parse them, so single quotes are the most efficient in defining strings

2, Double quotes 

  Variables contained in double quotes will be automatically Replace it with the variable value

3. Delimiter The delimiter is followed by specifying an identifier to indicate the beginning, and finally the same identifier ends the string
ˆEnd The identifier must start from the first column of the row, and cannot contain any other characters except a semicolon.

//字符串型
$str = '字符串型';
echo &#39;str是$str <br>&#39;;
//结果为 str是$str     单引号变量保持原样输出
echo "str是$str <br>";  
//结果为 str是字符串型  双引号会解析其中的变量
$str2 = <<<str2
这是定界符中的文字
str2;echo $str2;            
//结果为  这是定界符中的文字

3. Composite data type

Array (Array)

1. An array is a collection of related data, arranged in a specific way to form a whole
2. It can be the same data type or different data types
3. In PHP, the index of an array can be a number or a string

//相同类型元素
$array1 = array(1,3,5,7,9);
//不同类型元素                    
$array2 = array(1,'hello',true,3.14);
//索引是数字             
$array3 = array(1=>'a',2=>'b',3=>'c');
//索引是字符串                
$array4 = array('a'='苹果','b'=>'香蕉','c'=>'桔子');

4. Special data type

Resource 1. Resource is a special variable type that holds references to external data sources, such as files, database connections, etc., until the communication ends
2. The database persistent connection is a special resource. It will not be released by the garbage collection system and needs to be released manually.

empty (NULL)

1. The value assigned is Null

2. The variable has not been assigned a value
3. After the variable is assigned a value, use the unset() function to clear it

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