PHP strtolower() Function
PHP strtolower() Syntax
strtolower(string $string): stringPHP strtolower() Basic examples
echo strtolower("Hello WORLD");hello worldConverts all characters to lowercase.
PHP strtolower() Real-world usage
$email = "USER@EXAMPLE.COM";
echo strtolower($email);user@example.comNormalizes email addresses.
PHP strtolower() Edge cases
echo strtolower("ÄÖÜ");ÄÖÜNon-ASCII characters are not converted correctly.
PHP strtolower() Common mistakes
Using strtolower with UTF-8 text
strtolower does not support multibyte characters.
echo strtolower("ÄÖÜ");echo mb_strtolower("ÄÖÜ");Use mb_strtolower() for UTF-8 strings.
PHP strtolower() Frequently Asked Questions
What does strtolower() do in PHP?
strtolower() converts all alphabetic characters in a string to lowercase.
Is strtolower() multibyte-safe?
No, strtolower() is not multibyte-safe. Use mb_strtolower() for UTF-8 strings.
Does strtolower() modify the original string?
No, strtolower() returns a new string and does not modify the original variable unless reassigned.
What characters are affected by strtolower()?
Only alphabetic ASCII characters are converted. Numbers and symbols remain unchanged.
What is the difference between strtolower() and mb_strtolower()?
strtolower() handles ASCII only, while mb_strtolower() supports multibyte encodings like UTF-8.
Does strtolower() work with Unicode characters?
No, strtolower() may not correctly convert Unicode characters. Use mb_strtolower() instead.
Can strtolower() be used for case-insensitive comparison?
Yes, converting both strings to lowercase allows case-insensitive comparison.
Is strtolower() fast?
Yes, strtolower() is a fast built-in function optimized for performance.
What happens if the string is already lowercase?
strtolower() returns the string unchanged if it is already lowercase.
Can strtolower() handle arrays?
No, strtolower() works only on strings. Use array_map() to apply it to arrays.
What is a real-world use case of strtolower()?
strtolower() is commonly used for normalization, such as processing emails or usernames.
How to convert an entire string to lowercase safely?
Use mb_strtolower($string, "UTF-8") for safe lowercase conversion in multibyte strings.