PHP function introduction—strtoupper(): Convert string to uppercase

PHP function introduction—strtoupper(): Convert a string to uppercase

In PHP, we often deal with the case conversion of strings. Among them, the strtoupper() function is a very commonly used function, which can convert all letters in a string to uppercase. This article will introduce the use of strtoupper() function in detail and provide some code examples to help you better understand its usage.

Using the strtoupper() function is very simple. You only need to provide a string as a parameter of the function. The function will return a result after converting all lowercase letters in the string to uppercase. The following is the basic syntax of this function:

strtoupper(string $string): string

Parameter description:

• $string: The string to be converted.

Return value:

• Returns the string converted to uppercase.

Code example 1:

$str = "Hello World!";  // 定义一个字符串变量
$result = strtoupper($str);  // 调用strtoupper()函数将字符串转换为大写
echo $result;  // 输出结果为：HELLO WORLD!

In the above example, we first define a string variable $str, whose value is "Hello World! ". Then, we called the strtoupper() function and passed the variable $str as the parameter of the function. The strtoupper() function converts all lowercase letters in the string to uppercase letters and assigns the converted result to the variable $result. Finally, we output the results to the screen through the echo statement.

In addition to converting simple strings, the strtoupper() function can also be used to process strings containing multiple words, for example:

Code example 2:

$str = "this is a sentence.";  // 定义一个包含多个单词的字符串
$result = strtoupper($str);  // 调用strtoupper()函数将字符串转换为大写
echo $result;  // 输出结果为：THIS IS A SENTENCE.

In In the above example, we defined a string $str that contains multiple words, and its value is "this is a sentence." We call the strtoupper() function to convert the string to uppercase and assign the result to the variable $result. Finally, we use the echo statement to output the results to the screen.

It should be noted that the strtoupper() function can only convert alphabetic characters in the string to uppercase, but will not convert other characters (such as numbers, punctuation marks, etc.). Here is an example:

Code Example 3:

$str = "123ABC!@#";  // 定义一个字符串，包含数字和特殊字符
$result = strtoupper($str);  // 调用strtoupper()函数将字符串转换为大写
echo $result;  // 输出结果为：123ABC!@#

In the above example, we have defined a string $str, which contains numbers and special characters. We call the strtoupper() function to convert the string to uppercase and assign the result to the variable $result. However, since the strtoupper() function can only convert alphabetic characters, numbers and special characters will not be converted. Therefore, the output result is the same as the input string.

To sum up, the strtoupper() function can convert all lowercase letters in a string to uppercase. Its use is very simple, just provide a string as a parameter and return the result through the function. If the string contains numbers or special characters, the strtoupper() function will not convert them. I hope the introduction in this article can help you better understand and use the strtoupper() function.

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