//string to all uppercase
$string = "String with Mixed use of Uppercase and Lowercase";
//php string to uppercase
$string = strtoupper($string);
// = "STRING WITH MIXED USE OF UPPERCASE AND LOWERCASE"
<?php
$str = "Mary Had A Little Lamb and She LOVED It So";
$str = strtoupper($str);
echo $str; // muestra: MARY HAD A LITTLE LAMB AND SHE LOVED IT SO
?>
$lowercase = "this is lower case";
$uppercase = strtoupper($lowercase);
echo $uppercase;
setlocale(LC_CTYPE, 'de_DE.UTF8');
// be noted
echo strtoupper('Umlaute äöü in uppercase'); // outputs "UMLAUTE äöü IN UPPERCASE"
echo mb_strtoupper('Umlaute äöü in uppercase', 'UTF-8'); // outputs "UMLAUTE ÄÖÜ IN UPPERCASE"