How to convert lowercase string to uppercase in php-PHP Problem-php.cn

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");".

How to convert lowercase string to uppercase in php

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:

strtoupperConvert all characters in the string to uppercase (PHP 4, PHP 5, PHP 7, PHP 8)
mb_strtoupperConvert all characters in the string to uppercase (PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
mb_convert_caseConvert 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

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

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then Direct output:

How to convert lowercase string to uppercase in php

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

"; echo "转换后的：".strtoupper($str); ?>

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How to convert lowercase string to uppercase in php

2. mb_strtoupper

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

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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:

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How to convert lowercase string to uppercase in php

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

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3. mb_convert_case

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

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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:

"; // 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 ?>

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How to convert lowercase string to uppercase in php

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

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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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