PHP intercepts the function substr() that returns a string

Example

Return "world" from a string:

<?php
echo substr("Hello world",6);
?>

Definition and usage

The substr() function returns a part of the string.

Note: If the start parameter is negative and length is less than or equal to start, length is 0.

Syntax

substr(string,start,length)

Parameters	Description
string	Required. Specifies a part of the string to be returned.
start	Required. Specifies where in the string to begin. 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 numbers - Returns from the position of the start parameter Negative numbers - Returns from the end of the string

Technical details

Return value:	Returns the extracted part of the string, or FALSE if it fails , or return an empty string.
PHP Version:	4+
Change Log:	In PHP 5.2.2 to In version 5.2.6, if the start parameter indicates a negative truncation or an out-of-bounds position, FALSE is returned. Other versions get the string starting at the start position.

更多实例

实例 1

使用带有不同正负数的 start 参数：

<?php
echo substr("Hello world",10)."<br>";
echo substr("Hello world",1)."<br>";
echo substr("Hello world",3)."<br>";
echo substr("Hello world",7)."<br>";

echo substr("Hello world",-1)."<br>";
echo substr("Hello world",-10)."<br>";
echo substr("Hello world",-8)."<br>";
echo substr("Hello world",-4)."<br>";
?>

实例 2

使用带有不同正负数的 start 和 length 参数：

<?php
echo substr("Hello world",0,10)."<br>";
echo substr("Hello world",1,8)."<br>";
echo substr("Hello world",0,5)."<br>";
echo substr("Hello world",6,6)."<br>";

echo substr("Hello world",0,-1)."<br>";
echo substr("Hello world",-10,-2)."<br>";
echo substr("Hello world",0,-6)."<br>";
echo substr("Hello world",-2-3)."<br>";
?>

PHP实例代码如下:

$rest_1 = substr("abcdef", 2); // returns "cdef" 
$rest_2 = substr("abcdef", -2); // returns "ef" 
 
$rest1 = substr("abcdef", 0, 0); // returns "" 
$rest2 = substr("abcdef", 0, 2); // returns "ab" 
$rest3 = substr("abcdef", 0, -1); // returns "abcde" 
$rest4 = substr("abcdef", 2,0); // returns "" 
$rest5 = substr("abcdef", 2,2); // returns "cd" 
$rest6 = substr("abcdef", 2, -1); // returns "cde" 
$rest7 = substr("abcdef", -2,0); // returns "" 
$rest8 = substr("abcdef", -2,2); // returns "ef" 
$rest9 = substr("abcdef", -2,-1); // returns "e"

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