What are the functions that convert php to uppercase?

There are 5 functions to convert to uppercase: 1. strtoupper(), which can convert all the letters in the string to uppercase; 2. ucfirst(), which can convert the first letter of the string to uppercase ; 3. ucwords(), which can convert the first letter of each word in the string to uppercase; 4. mb_strtoupper(), etc.

The operating environment of this tutorial: windows7 system, PHP8.1 version, DELL G3 computer

In Web development, there is a lot of data that needs to be Regularity makes it easier for administrators to manage. Therefore, when storing some data, it is necessary to uniformly handle the upper and lower case of letters. However, in order to facilitate user input, users are not deliberately required to enter uppercase or lowercase letters. Instead, when storing data, program control is used to store the input content in uppercase or lowercase letters.

PHP provides us with a lot of predefined functions, including functions for converting strings to uppercase and lowercase. Here are the five built-in uppercase functions:

Function name	Function
strtoupper	Convert the string to uppercase
ucfirst	Convert the first letter of the string to uppercase
ucwords	Convert the first character of each word in the string to uppercase
mb_strtoupper	Convert the string to uppercase (different from the strtoupper function)
mb_convert_case	Convert strings according to different modes

1. strtoupper

strtoupper() function can convert the The letters are converted 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
    $str = "https://www.php.cn/";
    $str = strtoupper($str);
    echo $str;
?>

2、mb_strtoupper

The function of mb_strtoupper() function is similar to 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()])

Among them, $str is the string that needs to be converted. , $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).

<?php
    $str = "https://www.php.cn/";
    $str = mb_strtoupper($str);
    echo $str.&#39;<br>&#39;;
    $str = "Τάχιστη αλώπηξ βαφής ψημένη γη, δρασκελίζει υπέρ νωθρού κυνός";
    $str = mb_strtoupper($str, &#39;UTF-8&#39;);
    echo $str;
?>

3, ucfirst

ucfirst function can convert the first letter of the string into capital. The syntax format is as follows:

ucfirst($str)

Among them, $str is the string that needs to be converted.

<?php
    $str = &#39;hello world!&#39;;
    $str = ucfirst($str);
    echo $str.&#39;<br>&#39;;
    $str2 = &#39;HELLO WORLD!&#39;;
    $str2 = ucfirst(strtolower($str2));
    echo $str2;
?>

4. ucwords

ucwords() function can convert the first letter of each word in the string to uppercase. The syntax format is as follows:

ucwords($str)

Among them, $str is the string that needs to be converted.

<?php
    $str = &#39;hello world!&#39;;
    $str = ucwords($str);
    echo $str.&#39;<br>&#39;;
    $str2 = &#39;HELLO WORLD!&#39;;
    $str2 = ucwords($str);
    echo $str2;
?>

5. mb_convert_case

mb_convert_case() function can convert strings to upper and 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 one of MB_CASE_UPPER, MB_CASE_LOWER and MB_CASE_TITLE; $encoding is the character encoding of the parameter, which 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
    $str = &#39;hello world!&#39;;
    $str = mb_convert_case($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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