PHP English letter uppercase/Lowercase conversion function summary

This article mainly introduces several PHP uppercase/Lowercase conversion functions, which can be used to convert letters into uppercase/lowercase letters or all uppercase/lowercase letters. For more information, see converting the first letter of each word to uppercase: ucwords ()
The code is as follows: $ Foo = 'Hello world! ';
$ Foo = ucwords ($ foo); // Hello World!

$ Bar = 'Hello WORLD! ';
$ Bar = ucwords ($ bar); // hello world!
$ Bar = ucwords (strtolower ($ bar); // Hello World!
?>

The first letter is capitalized: ucfirst ()
The code is as follows: $ Foo = 'Hello world! ';
$ Foo = ucfirst ($ foo); // Hello world!

$ Bar = 'Hello WORLD! ';
$ Bar = ucfirst ($ bar); // hello world!
$ Bar = ucfirst (strtolower ($ bar); // Hello world!
?>

The first letter of a word becomes smaller: lcfirst ()
The code is as follows: $ Foo = 'helloworld ';
$ Foo = lcfirst ($ foo); // helloWorld

$ Bar = 'Hello WORLD! ';
$ Bar = lcfirst ($ bar); // hELLO WORLD!
$ Bar = lcfirst (strtoupper ($ bar); // hELLO WORLD!
?>

Uppercase for all letters: strtoupper ()
Write down all letters: strtolower ()