php中字母大小写转换函数_PHP教程

echo strtolower("Hello WORLD!");
?>

$str = "Mary Had A Little Lamb and She LOVED It So";
$str = strtoupper($str);
echo $str; // 打印 MARY HAD A LITTLE LAMB AND SHE LOVED IT SO
?>

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

 $foo = 'HelloWorld';
 $foo = lcfirst($foo);             // helloWorld
 
 $bar = 'HELLO WORLD!';
 $bar = lcfirst($bar);             // hELLO WORLD!
 $bar = lcfirst(strtoupper($bar)); // hELLO WORLD!
 ?>