// The array contains only numbers and alphabets.
$morse = [
	"A" => ".-","B" => "-...","C" => "-.-.","D" => "-..",
	"E" => ".","F" => "..-.","G" => "--.","H" => "....",
	"I" => "..","J" => ".---","K" => "-.-","L" => ".-..",
	"M" => "--","N" => "-.","O" => "---","P" => ".--.",
	"Q" => "--.-","R" => ".-.","S" => "...","T" => "-",
	"U" => "..-","V" => "...-","W" => ".--","X" => "-..-",
	"Y" => "-.--","Z" => "--..",1 => ".----",2 => "..---",
	3 => "...--",4 => "....-",5 => ".....",6 => "-....",
	7 => "--...",8 => "---..",9 => "----.",0 => "-----",
];
function convert_text_to_morse($str){
	global $morse;
	$result = "";
	for ( $i = 0; $i < strlen($str); $i++ ){
		if( $str[$i] == " " ) $result .= " / ";
		else {
			$result .= $morse[strtoupper($str[$i])]." ";
		}
	}
	return $result;
}
// print_r ($morse);
echo convert_text_to_morse("Hello world");
// outputs:   .... . .-.. .-.. ---  / .-- --- .-. .-.. -.. 
echo "\n";
echo convert_text_to_morse("404 ERROR");
// outputs :   ....- ----- ....-  / . .-. .-. --- .-.