Detailed explanation of PHP string self-calculation and numerical calculation usage

伊谢尔伦
Release: 2023-03-10 22:24:01
Original
1813 people have browsed it

When a string is treated as a numerical value, the result and type are as follows:

If the string does not contain '.', 'e' or 'E ' and its numeric value is within the range of integer types (defined by PHP_INT_MAX), the string will be evaluated as integer. In all other cases the value is treated as float.

The beginning of the string determines its value. If the string begins with a legal numeric value, that numeric value is used. Otherwise its value is 0 (zero). Legal values ​​consist of an optional sign, followed by one or more digits (possibly with a decimal point), and then an optional exponent part. The exponent part consists of an ‘e’ or ‘E’ followed by one or more digits.

The following will be converted into an integer:

[+/-][0-9][*]
Copy after login

The following will be converted into a floating point typenumber:

[+/-][0-9][.][0-9][e/E][0-9][*]
Copy after login
$r = '123' + 1;
var_dump($r);// 输出结果 int(124)$r = '123.4' + 1;
var_dump($r);// 输出结果 float(124.4)$r = '1.5e4' + 1;
var_dump($r);// 输出结果 float(15001)$r = '123456789123456789' + 1;
var_dump($r);// 输出结果 float(1.2345678912346E+17)$r = '123abc' + 1;
var_dump($r);// 输出结果 int(124)$r = '123e1abc' + 1;
var_dump($r);// 输出结果 float(1231)$r = '123.abc' + 1;
var_dump($r);//输出结果 float(124)$r = '+123abc' + 1;
var_dump($r);// 输出结果 int(124)$r = '-123abc' + 1;
var_dump($r);// 输出结果 int(-122)$r = 'abc' + 1;
var_dump($r);// 输出结果 int(1)
Copy after login

It has been determined that an integer is required ( floating point number), you can use intval() (floatval()) to first convert the string into an integer (floating point number), and then perform calculations with other values.

one. Addition of numeric strings in PHP

1. If the two strings do not have a valid value at the beginning or are not numeric strings, the two strings will be regarded as 0 when added;

$a="abc";
$b="b01";
$a+$b是0
Copy after login

2. When adding two numerical strings, the significant digits are added.

$a="100";
$b="01a";
$a+$b=101;
Copy after login

3/If the string contains ‘.’, ‘e’, ‘E’, it will be processed as a float type number.

$a="100";
$b="12.6a";
$a+$b=112.6;
Copy after login
$a='10';
$b='12.3e3';
$a+$b同样为float型float(12310)
Copy after login

Compare two strings in 2.php (< > ==);

Compare two strings in 1.php to see if they are equal, Generally, (==) is not used, because (==) will change the original data type , but use the strcmp(str1, str2) series of functions strcmp($str1,$str2);(strcmp It is forced to convert to string type for comparison).

$a=&#39;123&#39;;
$b=&#39;123.&#39;;($b后多了一个小数点)
Copy after login

But when compared with (==), the result is true

var_dump($a==$b);

So it is generally not used (= =) Compare strings.

In addition, when a number is compared with a string, the string will be converted to int or float type (numberic_string contains ‘.’, ‘e’, ‘E’).

‘abc’转化为int(0);
‘12ab’转化为int(12);
‘12.3e3&#39;转化为float(12300);
Copy after login

2. Comparison of (> <)

2-1: If it is a comparison of two strings, compare the ASCII codes of the corresponding characters one by one.

2-2: If numbers are compared with strings, the strings are first converted into numbers and then compared.

2-3: If two numeric strings (pure numeric strings) are compared, the two strings are first converted into numbers and then compared.

$a=&#39;100&#39;;
$b=&#39;20&#39;;
则$a>$b;
Copy after login

But

如$a=&#39;&#39;100a;
$b=&#39;20&#39;;时,
结果为$a<$b;
Copy after login

The above is the detailed content of Detailed explanation of PHP string self-calculation and numerical calculation usage. For more information, please follow other related articles on the PHP Chinese website!

source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template
About us Disclaimer Sitemap
php.cn:Public welfare online PHP training,Help PHP learners grow quickly!