How to replace part of a string using substr_replace function in PHP

In PHP development, we often need to replace part of the content in the string. PHP provides a built-in function substr_replace(), which can be used to implement this function.

The basic syntax of the substr_replace() function is as follows:

substr_replace ( string $string , string $replacement , mixed $start [, mixed $length ] ) : string

Parameter description:

• $string: The string that needs to be replaced.
• $replacement: replacement content.
• $start: Specifies the starting position of the replacement, which can be a negative number, indicating the offset calculated from the end of the string.
• $length: Optional parameter, specifying the number of characters to be replaced.

The following is a sample code that uses the substr_replace() function to implement string replacement:

<?php
$str = "Hello World";
$new_str = substr_replace($str, "PHP", 0, 5);
echo $new_str;  // PHP World
?>

In the above code, we replace the first 5 characters in the string $str with "PHP", got the new string $new_str.

The following introduces several common string replacement application scenarios and how to use the substr_replace() function to achieve replacement:

1. Replace spaces in strings

Sometimes We need to replace the spaces in the string with other characters, such as underscore or underscore. This can be achieved using the substr_replace() function.

<?php
$str = "Hello World";
$new_str = substr_replace($str, "-", strpos($str, " "), 1);
echo $new_str;  // Hello-World
?>

In the above code, we use the strpos() function to find the position of the space, and then use the substr_replace() function to replace it with a underscore.

2. Replace specific characters in a string

Sometimes we need to replace a specific character in a string with other characters. This can be achieved using the substr_replace() function.

<?php
$str = "Hello World";
$new_str = substr_replace($str, "!", strpos($str, " "));
echo $new_str;  // Hello! World
?>

In the above code, we use the strpos() function to find the position of the space, and then use the substr_replace() function to replace it with an exclamation mark.

3. Replace a piece of content in a string

Sometimes we need to replace a piece of content in a string with other characters. This can be achieved using the substr_replace() function.

<?php
$str = "Hello World";
$new_str = substr_replace($str, "PHP", 0, 5);
echo $new_str;  // PHP World
?>

In the above code, we use the substr_replace() function to replace the first 5 characters in the string $str with "PHP" and get the new string $new_str.

Summary

The substr_replace() function is a very practical string replacement function in PHP, which can replace part of the content in a string. In actual development, you can use the substr_replace() function to replace strings according to the application scenario to improve development efficiency.

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