How to convert string to uppercase in PHP

php editor Banana today will introduce to you how to convert a string into uppercase. In PHP, you can use the built-in function strtoupper() to achieve this function, which converts all letters in the string to uppercase. This function is very practical, especially suitable for scenarios that require a unified string format. Next, we will explain in detail how to use the strtoupper() function to convert a string into uppercase, so that you can easily master this skill during development.

phpConvert string to uppercase

In PHP, converting a string to uppercase is a common operation. This article will introduce several methods in detail to help you easily convert strings to uppercase.

Method 1: strtoupper() function

This is the most common method, just pass the string as a parameter to the strtoupper() function.

$str = "hello world";
$upperCaseStr = strtoupper($str);

echo $upperCaseStr; // Output: HELLO WORLD

Method 2: mb_strtoupper() function

This function is the multibyte version of the strtoupper() function, suitable for non-ASCII character sets.

$str = "Hello world";
$upperCaseStr = mb_strtoupper($str);

echo $upperCaseStr; // Output: Hello world (uppercase) 

Method 3: Use built-in constants

PHP provides the built-in constant STR_TO_UPPER, which can be used to convert a string to uppercase.

$str = "hello world";
$upperCaseStr = strtr($str, "abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ");

echo $upperCaseStr; // Output: HELLO WORLD

Method 4: Use preg_replace() function

preg_replace() The function can be used to replace lowercase characters in a string with uppercase characters using regular expressions.

$str = "hello world";
$upperCaseStr = preg_replace("/[a-z]/", strtoupper("$0"), $str);

echo $upperCaseStr; // Output: HELLO WORLD

Method 5: Use array_map() function

array_map() The function can be used to convert each element in an array to uppercase.

$str = "hello world";
$strArr = str_split($str);
$upperCaseArr = array_map("strtoupper", $strArr);
$upperCaseStr = implode("", $upperCaseArr);

echo $upperCaseStr; // Output: HELLO WORLD

Summarize

The above methods can effectively convert PHP strings to uppercase. Which method you choose depends on your string's special requirements and performance considerations.

method	Advantage	Disadvantages
strtoupper()	Easy to use	Non-ASCII character sets are not supported
mb_strtoupper()	Support multi-byte character sets	Slower than strtoupper()
Built-in constants	Reliable and efficient	Multi-byte character sets are not supported
preg_replace()	Flexible and powerful	The performance overhead is higher than other methods
array_map()	Applies to string arrays	Requires string splitting and reassembly

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