$str = array("ABC123", 'ABC', 'XYz');
foreach ($str as $s)
{
if (ctype_upper($s))
echo "string: $s - include only uppercase characters <br />";
else
echo "string: $s - NOT include only uppercase characters <br />";
}
/*
run:
string: ABC123 - NOT include only uppercase characters
string: ABC - include only uppercase characters
string: XYz - NOT include only uppercase characters
*/