Basic tutorial for getting started with PHP - PHP data types

Syntax: Integer values ​​can be expressed in decimal, hexadecimal or octal notation, and may be preceded by an optional sign (- or +). Octal represents a number that must be preceded by 0 (zero), and hexadecimal represents a number that must be preceded by 0x.

Example 1,

<?php
//php数据类型
//by bbs.it-home.org
$int1=100; //十进制
$int2=-123; //负数
$int3=0123; //八进制数
$int4=0x1A;//十六进制数

echo PHP_INT_SIZE; //显示一个整数用几个字节来表示
echo "<br/>";
echo PHP_INT_MAX;echo "<br/>";//整数最大有多少数 （2147483647）
$fmax=2147483648;
var_dump(PHP_INT_MAX); //一个数超出了 integer 的范围，将会被解释为 float类型。
echo "<br/>";
var_dump($fmax);
?>

Floating point number: Floating point number (double precision number or real number)

<?php
$a=1.34;
$b=1.8e308;
$c=8e-10; 
var_dump($b);
//浮点数的字长和平台相关，尽管通常最大值是 1.8e308 并具有 14 位十进制数字的精度(不能超过14位)
//精度要从左边开始的第一个非0的数字计算.

//如：
$a=567.9999899   //输出567.9999899
$b=789.8812345678543   //输出789.88123456785
$c=0.000000008907777777 //输出0.000000008907777777
?>

Important understanding: The accuracy is calculated from the first non-0 number starting from the left. The Boolean type is the simplest type in PHP. Its value can be TRUE or FALSE. Such as:

<?php
$foo=false;
$foo1=true;
echo "为假时输出值为:".$foo; //没有输出值
echo "<br />为真时输出值为:".$foo1; //输出1

Details: When converted to boolean, the following values ​​are considered FALSE: 1. the Boolean value FALSE itself 2. the integer value 0 (zero) 3. The floating point value 0.0 (zero), the empty string, and the string "0" 4. Array not containing any elements 5. Objects that do not include any member variables (only applicable to PHP 4.0) 6. Special type NULL (including variables that have not been set) 7. SimpleXML objects generated from XML documents without any tags

<?php
//$a=0;
//$a=0.0;
$a="0";
var_dump((bool) 0);
echo "<br />";
var_dump((bool) array());
if($a==false){
echo "空0默认转换为false，成功！";
}else{
echo "不能转换为false";
}

Output: bool(false) bool(false) Empty 0 is converted to false by default, success!

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