How to convert lowercase string to uppercase in php

3 methods: 1. Use strtoupper() to convert all characters in the string to uppercase, the syntax is "strtoupper($str)"; 2. Use mb_strtoupper() to convert, the syntax is "mb_strtoupper($ str,"UTF-8")"; 3. Use mb_convert_case() to convert, the syntax is "mb_convert_case($str,MB_CASE_UPPER,"UTF-8");".

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

Convert string lowercase to uppercase in PHP There are three functions, namely:

• strtoupper Convert all characters in the string to uppercase (PHP 4, PHP 5, PHP 7, PHP 8)

• mb_strtoupper Convert all characters in the string to uppercase (PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

• mb_convert_case Convert strings according to different modes (PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)

These three functions and their usage are explained in detail below.

1. strtoupper

strtoupper(string $string): string

This function directly returns the upper case of the incoming string, for example:

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);  
echo strtoupper("Hello WORLD!");
?>

then Direct output:

Of course, you can also use variables to receive the output value, such as:

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

2. mb_strtoupper

mb_strtoupper(string $str, string $encoding = mb_internal_encoding()): string

This function has an additional character encoding parameter encoding. If it is omitted or null, the internal character encoding is used. The string to be converted to uppercase is $str.

The difference from strtoupper() above is that the "letter" is determined through the Unicode character attribute. Therefore, this function is not affected by the locale setting and can convert any character with a "letter" attribute. For example, a diacritical mark (ä) can also be converted, but strtoupper() cannot.

Example:

<?php
$str = "Mary Had A Little Lamb and She LOVED It So";
$str = mb_strtoupper($str);
echo $str; // 打印的是 MARY HAD A LITTLE LAMB AND SHE LOVED IT SO
?>

In the case of Ferdinand, you can refer to this example:

<?php
$str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
$str = mb_strtoupper($str, &#39;UTF-8&#39;);
echo $str; // 打印的是 ΤΆΧΙΣΤΗ ΑΛΏΠΗΞ ΒΑΦΉΣ ΨΗΜΈΝΗ ΓΗ, ΔΡΑΣΚΕΛΊΖΕΙ ΥΠΈΡ ΝΩΘΡΟΎ ΚΥΝΌΣ
?>

3. mb_convert_case

mb_convert_case(string $str, int $mode, string $encoding = mb_internal_encoding()): string

The third function is mb_convert_case. This function has one more mode parameter than the previous function mb_strtoupper.

The conversion mode of mb_convert_case is determined by mode. The value of this parameter can be one of the following three.

• MB_CASE_UPPER —— Convert to uppercase

• ##MB_CASE_LOWER —— Convert to lowercase

• MB_CASE_TITLE — — Convert the first letter of the word to uppercase

Example:

<?php
$str = "mary had a Little lamb and she loved it so";
$str = mb_convert_case($str, MB_CASE_UPPER, "UTF-8");
echo $str."<br>"; // 输出 MARY HAD A LITTLE LAMB AND SHE LOVED IT SO
$str = mb_convert_case($str, MB_CASE_TITLE, "UTF-8");
echo $str; // 输出 Mary Had A Little Lamb And She Loved It So
?>

The same is true for non-Latin characters, the example is as follows:

<?php
$str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
$str = mb_convert_case($str, MB_CASE_UPPER, "UTF-8");
echo $str; // 输出 ΤΆΧΙΣΤΗ ΑΛΏΠΗΞ ΒΑΦΉΣ ΨΗΜΈΝΗ ΓΗ, ΔΡΑΣΚΕΛΊΖΕΙ ΥΠΈΡ ΝΩΘΡΟΎ ΚΥΝΌΣ
$str = mb_convert_case($str, MB_CASE_TITLE, "UTF-8");
echo $str; // 输出 Τάχιστη Αλώπηξ Βαφήσ Ψημένη Γη, Δρασκελίζει Υπέρ Νωθρού Κυνόσ
?>

The above are the three methods in PHP to convert lowercase letters in a string to uppercase letters. It can be seen that the simplest method is the first method, which only needs to pass in the string, and the second method is more Regarding the encoding settings, the most complicated one is the third one. In addition to converting to uppercase, it can also be converted to lowercase and the first letter is capitalized.

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