Easy string to array conversion

As you may know, in the C language a string is in fact an array of characters, terminated by the null character \0.
In PHP, the idea is still here but it’s a little bit different. Strings are not considered as array but each characters are easily reachable using the following syntax :

$str = 'Hello World!';
$char = $str{4};

echo $char; // output : o

So, you may iterate on string characters to build an array :

$str = 'Hello World!';
$n = strlen($str);
$arr = array();
for ($i = 0; $i < $n; $i++){
    $arr[$i] = $str{$i};
}

But, it’s by far not the easiest way to convert a string into an array
PHP has already a built-in function to do the job : str_split.

$str = 'Hello World!';
$arr = str_split($str);

print_r($arr);
/*
Array
(
    [0] => H
    [1] => e
    [2] => l
    [3] => l
    [4] => o
    [5] =>
    [6] => W
    [7] => o
    [8] => r
    [9] => l
    [10] => d
    [11] => !
)
*/

Plus, str_split has another cool feature : if the optional second parameter is specified, the returned array will be broken down into chunks with each the length you have chosen.

$str = 'Hello World!';
$arr = str_split($str, 2);

print_r($arr);
/*
Array
(
    [0] => He
    [1] => ll
    [2] => o
    [3] => Wo
    [4] => rl
    [5] => d!
)
*/

Now, let’s make an example with a very simple string to hexadecimal representation function :

function str_to_hex($str)
{
    $n = strlen($str);
    $str = str_split($str);
    for ($i = 0; $i < $n; $i++){
        $str[$i] = dechex(ord($str[$i]));
    }
    return implode($str);
}

echo str_to_hex('Hello'); // output : 48656c6c6f

The reverse :

function hex_to_str($str)
{
    $str = str_split($str, 2);
    $n = sizeof($str);
    for ($i = 0; $i < $n; $i++){
         $str[$i] = chr(hexdec($str[$i]));
    }
    return implode($str);
}

echo hex_to_str('48656c6c6f'); // output : Hello

Enjoy