Convert a number from lower case to upper case in php

In the process of PHP programming, it often involves the need to convert a number into uppercase letters. This situation often occurs when operating in invoicing, finance and other fields. The PHP language provides a function library for us to implement this operation.

In the PHP language, there is a very convenient function that can convert numbers into uppercase letters. The function is chr() . The parameter of this function is a decimal number, and it returns the ASCII character corresponding to the number.

In computer programming, each character has a corresponding ASCII code. We can use the ASCII code table to convert characters and numbers. ASCII code is a type of character encoding. It is the most widely used character encoding standard and can represent 256 different characters.

Based on this principle, we can convert numbers into letters through a certain algorithm. Below is a PHP code demonstration that converts lowercase numbers to uppercase letters.

function toUpperLetter($num){
    //将数字转换为字符串
    if(!is_numeric($num)){
        return false;
    }
    $num = strval($num);
    
    //一个字母对应的数字范围
    $asciiA = ord('a'); //97
    $asciiZ = ord('z'); //122
    
    $result = '';
    $len = strlen($num);
    for($i = 0; $i < $len; $i++){
        $ascii = ord(substr($num, $i, 1));
        if($ascii >= $asciiA && $ascii <= $asciiZ){
            $result .= chr($ascii - 32);
        } else {
            $result .= substr($num, $i, 1);
        }
    }
    return $result;
}

In the above code, the toUpperLetter() function accepts a number as a parameter and returns uppercase letters in string form.

The principle of this algorithm is: by looping through the input numbers, judge the ASCII code corresponding to each number. If it is within the range of lowercase letters a~z, subtract 32 from its value. , that is, converted to the ASCII code of the letter, converted into characters through the chr() function, and finally returned as a string.

When we use toupperLetter(1234), the result we get is: ONE TWO THREE FOUR. This is exactly what we expected.

In the actual development process, if we need to convert numbers into uppercase letters, we can directly call the above function to complete the operation quickly and accurately.

In short, the chr() function of PHP language can help us obtain the corresponding characters from the ASCII code, and then realize the function of converting numbers into uppercase letters, which can improve development efficiency in some fields such as finance and invoices.

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