How to convert all php strings to uppercase

Conversion methods: 1. Use strtoupper() function for conversion, syntax "strtoupper(string)"; 2. Use mb_strtoupper() function for conversion, syntax "mb_strtoupper(string, character encoding)" ;3. Use the mb_convert_case() function to convert, the syntax is "mb_convert_case(string, MB_CASE_UPPER, character encoding)".

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

In PHP, you want to convert a string into Convert all letters to lowercase, you can use the following 3 functions:

Function name	Function
strtoupper	Converts all the characters in the string to uppercase
mb_strtoupper	Converts all the characters in the string to uppercase (similar to the strtoupper function There are differences)
mb_convert_case	Convert strings according to different modes

Method 1: Use strtoupper() function for conversion

strtoupper() function can convert letters in the string to uppercase. The syntax format is as follows:

strtoupper($string)

Among them, $string is a parameter of string type. This function can convert the letters in the parameter $string to uppercase and return the converted string.

<?php
header("Content-type:text/html;charset=utf-8");
$str = "https://www.php.cn/";
echo "原字符串：<br> $str <br><br>";
$str = strtoupper($str);
echo "转换后：<br> $str";
?>

Method 2: Use mb_strtoupper() function for conversion

Function of mb_strtoupper() function Similar to the strtoupper() function, the letters in the string can also be converted to uppercase, and the mb_strtoupper() function can also set the character encoding of the parameter. The syntax format is as follows:

mb_strtoupper($str [, $encoding = mb_internal_encoding()])

where, $ str is the string that needs to be converted, and $encoding is an optional parameter used to set the character encoding of the parameter.

The difference from the strtoupper() function is that the letters in $str are determined through the Unicode character attribute. Therefore, the mb_strtoupper() function is not affected by the locale setting and can convert any character with a "letter" attribute, such as a umlaut (ä).

Example 1:

<?php 
header(&#39;content-type:text/html;charset=utf-8&#39;);  
$str = "hello";
echo "原字符串：<br> $str <br><br>";
$str = mb_strtoupper($str, &#39;UTF-8&#39;);
echo "转换后：<br> $str";
?>

Example 2:

<?php
header("Content-type:text/html;charset=utf-8");
$str = "τάχιστη αλώπηξ βαφήσ ψημένη γη, δρασκελίζει υπέρ νωθρού κυνόσ";
echo "原字符串：<br> $str <br><br>";
$str = mb_strtoupper($str, &#39;UTF-8&#39;);
echo "转换后：<br> $str";
?>

Method 3: Use the mb_convert_case() function to convert

The mb_convert_case() function can convert strings from upper to lower case. The syntax format is as follows :

mb_convert_case($str, $mode [, $encoding = mb_internal_encoding()])

Among them, $str is the string that needs to be converted; $mode is the conversion mode, which can be MB_CASE_UPPER (all converted to uppercase), MB_CASE_LOWER (all One of MB_CASE_TITLE (convert the first letter to uppercase); $encoding is the character encoding of the parameter and can be omitted.

Compared with the strtolower() and strtoupper() functions, the mb_convert_case() function performs case conversion based on Unicode character attributes. Therefore, the behavior of the mb_convert_case() function is not affected by the locale setting and can convert any character with a "letter" attribute, such as the umlaut A (Ä).

<?php
header("Content-type:text/html;charset=utf-8");
$str = &#39;Hello world!&#39;;
echo "原字符串：<br> $str <br><br>";

echo "转换后：<br>";
$str = mb_convert_case($str, MB_CASE_UPPER, "UTF-8");
echo $str.&#39;<br>&#39;;
$str = mb_convert_case($str, MB_CASE_LOWER, "UTF-8");
echo $str.&#39;<br>&#39;;
$str = mb_convert_case($str, MB_CASE_TITLE, "UTF-8");
echo $str.&#39;<br>&#39;;
?>

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