PHP: Introduction to the usage differences between substr and substring

Everyone knows that the string interception characters in js have functions substr and sub string, what about PHP? PHP does not have a directly available substring function, but it does have a substr function.

If you don’t believe it, you can test it yourself. A correct piece of code is given below.

<?
$a="me";
echo(substr($a,,));//输出me
?>
下面又给出一段错误的代码
<?
$a="me";
echo(subString($a,,));
?>

substr() function returns a part of a string.

substr(string,start,length)

string: The string to be intercepted

start:

Positive number - starts at the specified position in the string
Negative number - starts at the specified position from the end of the string
0 - starts at the first character in the string

length:

Optional. Specifies the length of the string to be returned. The default is until the end of the string.
Positive number - Return from the position of the start parameter
Negative number - Return from the end of the string

Detailed explanation of the usage of PHP substr()

Definition and usage

提示和注释

注释：如果 start 是负数且 length 小于等于 start，则 length 为 0。

例子

<?php
$str = &#39;hello world!&#39;;
echo substr($str, 4); // o world! 左起第4开始向右截取到末尾
echo substr($str, 4, 5); // o wor 左起第4开始向右取5位
echo substr($str, 4, -1); // o world 左起第4与右起第1之间的字符
echo substr($str, -8, 4); // o wo 右起第8开始向右截取4位
echo substr($str, -8,-2); // o worl 右起第8与右起第2之间的字符
?>

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