How to convert string to lowercase with PHP

In web development, PHP is one of the most numerous server-side scripting languages. For PHP developers, sometimes it is necessary to convert string case to uppercase and lowercase. In this article, we will take a deep dive into how to convert a string to lowercase in PHP.

In PHP, there are multiple ways to convert a string to lowercase. Here are some of the methods:

1. strtolower() function

The strtolower() function can convert a string to lowercase letters. The syntax of this function is as follows:

string strtolower (string $string)

Among them, the $string parameter is the string to be converted.

The following is sample code to convert a string to lowercase using the strtolower() function:

$str = "PHP 转小写";
echo strtolower($str);

Output:

php 转小写

2. mb_strtolower() function

mb_strtolower() function is a function in the mbstring function extension, which can convert strings to lowercase letters and supports multi-byte character sets. The syntax of this function is as follows:

string mb_strtolower (string $str [, string $encoding = mb_internal_encoding()])

Among them, the $str parameter is the string to be converted, the $encoding parameter is the character set encoding, and the default value is mb_internal_encoding().

The following is sample code to convert a string to lowercase using the mb_strtolower() function:

$str = "PHP 转小写";
echo mb_strtolower($str);

Output:

php 转小写

3. strtolower() and mb_strtolower The difference between ()

Although both methods can convert strings to lowercase letters, the strtolower() function only supports single-byte character sets, while the mb_strtolower() function not only supports Single-byte character set, also supports multi-byte character sets, such as UTF-8, etc.

4. Custom function

In addition to the built-in functions, you can also customize functions to convert PHP strings to lowercase. The following is a sample code for a custom function:

function toLower($str) {
    $res = "";
    for ($i = 0; $i < strlen($str); $i++) {
        $char = ord($str[$i]); // 将字符转换为ASCII码
        if ($char >= 65 && $char <= 90) { // 判断字符是否为大写字母
            $res .= chr($char + 32); // ASCII码加32，得到对应的小写字母
        } else {
            $res .= $str[$i]; // 如果不是大写字母，直接拼接上去
        }
    }
    return $res;
}

$str = "PHP 转小写";
echo toLower($str);

Output:

php 转小写

Summary

This article introduces several ways to convert PHP to lowercase letters Methods, including using the built-in functions strtolower() and mb_strtolower(), as well as custom functions. To ensure code portability and multi-language support, it is recommended to use the mb_strtolower() function.

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