By default, array_search performs the same comparison as the == operator, which will attempt to "type juggle" certain values. For instance, '1' == 1, '1.' == 1, and '1.' == '1' are all true.

That means that '1' and '1.' will always match the same element in your lookup table.

Luckily, the function takes a third argument, which the manual describes as:

If the third parameter strict is set to true then the array_search() function will search for identical elements in the haystack. This means it will also perform a strict type comparison of the needle in the haystack, and objects must be the same instance.

This makes it equivalent to the === operator instead. Note that '1' === 1, '1.' === 1, and '1.' === '1' are all false.

So you just need to add that argument:

echo array_search($char,$dict,true);

You just need to do a strict search.

See 3rd parameter of array_search.

function decode($cypher,$dict){

    $sepp = explode(" ",$cypher);

    foreach($sepp as $char){
      echo array_search($char,$dict,true);
    }
}

The reason it doesn't work without is because php thinks 1 and 1. is the same number.

This line would help you. Set third parameter to true. This causes the comparison to run in strict mode.

echo array_search($char, $dict, true);

function decode($cypher, $dict)
{
    $sepp = explode(" ",$cypher);
    foreach ($sepp as $char) {
        echo array_search($char, $dict, true);
   }
}