1.PHP has eight variable types:

<1>Scalar type:

boolean (Boolean)

integer (integer)

float (floating point type, also called "double")

string (string)

<2>Composite type:

array (array)

object (object)

<3> Special types:

resource (resource)

NULL

PS: PHP variable type is not used Statement, PHP will automatically determine its type based on the context in which the program is running. Isn’t it smart? So awesome

If you want to check the value of an expression and similar, you can use the function var_dump().

(1).boolean (Boolean type)

There are only two values, true or false, which are not case-sensitive. All non-0 values ??are is true, 0 is false.

boolean (Boolean type) is often used for conditional judgment in process control.

Example:

[php]  
<?php  
$b=true;  
if ($b == true)  
{  
    echo &#39;$b is true&#39;;  
}  
?>

2.integer (integer)

Integer values ??can be specified in decimal, hexadecimal or octal notation

Example:

<?php
$b = 1234; // 十進(jìn)制數(shù)
$b = -123; // 一個(gè)負(fù)數(shù)
$b = 0123; // 八進(jìn)制數(shù)（等于十進(jìn)制的 83）
$b = 0x1A; // 十六進(jìn)制數(shù)（等于十進(jìn)制的 26）

?>

3.float (floating point type, also called "double")

Floating point number ( Also called floats, doubles or real numbers) can be defined with any of the following syntax:

Example:

[php]  
<?php  
$b = 1.334;  
$b = 1.3e3;  
$b = 8E-10;  
?>

(4)string( String)

String definitions are divided into three ways: single quotes, double quotes, and delimiters.

For example:

[php]  
<?php  
//單引號(hào)定義字符串  
$a = &#39;aaa&#39;;  
//雙引號(hào)定義字符串  
$b = "bbb";  
//定界符定義字符串  
$c = <<<eof  
ccccccccc  
eof;//頂?shù)筋^開始寫，前面不能留空格  
echo $a;  
echo "<br>";  
echo $b;  
echo "<br>";  
echo $c;  
?>

Variable analysis:

Single quotes: If the definition content includes variables, the variable name is output directly instead of the content.

Double quotation marks: If the definition content includes variables, the content will be output directly.

delimiter: If the definition content includes variables, the content will be output directly.

In double quotes and delimiters, {} can be used to specify variable scope.

[php]  
<?php  
$temps = "123";  
$tempss = "1234";  
$b = "bbb{$temps}s";  
echo $b;  
?>

(5)array() (array) definition

array( [key =>]

value

, ...

)

// key Can be integer or string

// value can be any value

For example:

[php]  
<?php  
$arr = array("foo" => "bar", 12 => true);  
echo $arr["foo"]; // bar  
echo $arr[12];    // 1  
?>

(6)object (object)

To initialize an object, use the new statement to instance the object to in a variable.

Example:

[php] 
<?php  
//創(chuàng)建一個(gè)foo的類  
class foo  
{  
    //創(chuàng)建一個(gè)do_foo的方法  
    function do_foo()  
    {  
        //輸出Dong Foo  
        echo "Doing foo.";  
    }  
}  
//創(chuàng)建一個(gè)$bar的實(shí)例  
$bar = new foo;  
//$bar的實(shí)例調(diào)用do_foo的方法  
$bar->do_foo();  
?>

(7)resource( Resources)

To be written. . .

(8)NULL

The special NULL value means that a variable has no value, not that the variable does not exist. The only possible value of type NULL is NULL. ‘

A variable is considered NULL when:

is assigned a value of NULL.

has not been assigned a value.

is unset().

For example:

[php]  
<?php  
$var = NULL;  
?>

Two related functions ：

is_null(): Determine whether the variable is NUll

unset(): Delete the variable declaration

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