How to replace the penultimate character in a string in php

In PHP, you can use the substr_replace() function to replace the penultimate character of the string; this function can replace the specified number of characters starting from the specified position in the string, and only needs to pass the third parameter Set to "-2", and the fourth parameter is set to 1 to replace the penultimate character. The syntax is "substr_replace(string, replacement value,-2,1)".

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

How to replace the penultimate digit of a string in php character? Simple, just use the substr_replace() function.

The substr_replace() function can replace the specified number of characters starting from the specified position in the string.

This function accepts 4 parameters, syntax:

substr_replace(string,replacement,start,length)

Parameters	Description
string	Required. Specifies the string to check.
replacement	Required. Specifies the string to be inserted.
start	Required. Specifies where in the string to begin replacement. Positive number - starts at the specified position in the string Negative number - starts at the specified position from the end of the string 0 - at the first character in the string Start at
length	Optional. Specifies how many characters to replace. The default is the same as the string length. Positive number - the length of the string to be replaced Negative number - the number of characters to be replaced from the end of the string 0 - insert instead of replace

#If start is a positive number, replacement will start from the start position of string. If start is negative, the replacement will start at the start position from the bottom of string.

If the length parameter is set and is a positive number, it represents the length of the replaced substring in string. If set to a negative number, it represents the number of characters from the end of the substring to be replaced from the end of string. If this parameter is not provided, the default is strlen(string) (the length of the string). Of course, if length is 0, then the function of this function is to insert replacement at the start position of string.

If you want to replace the penultimate character of the string, you only need to set the third parameter to "-2" and the fourth parameter to 1.

Example:

<?php
header("content-type:text/html;charset=utf-8");
$str = &#39;hello&#39;;
echo "原字符串：".$str."<br><br>";
$replace = &#39;A&#39;;
echo "替换倒数第二个字符后：".substr_replace($str, $replace, -2,1);
?>

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