capital letter php

PHP
$str = strtolower($str);$lowercase = "this is lower case";
$uppercase = strtoupper($lowercase);

echo $uppercase;
// THIS IS LOWER CASE<?php
$foo = 'hello world!';
$foo = ucfirst($foo);             // Hello world!

$bar = 'HELLO WORLD!';
$bar = ucfirst($bar);             // HELLO WORLD!
$bar = ucfirst(strtolower($bar)); // Hello world!
?>
// string manipulation function 

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