How do I replace a specific position (X,Y) in a string with multiple lines? (PHP)-CodePudding

I've got a field 30x7 (see below) and I want to replace a specific position.
The position is randomly given and I want to replace the random position (X,Y) with a letter.
I already got the field and the replacement but it's not exactly what I want.

 $field=('################################')."\n".str_repeat.('#                              #\n', 7)('################################')."\n"

`
The field will look like this

##############################   
#                            #  
#                            #  
#                            #  
#                            #  
#                            #  
#                            #  
#                            #  
##############################

and the empty space at the given position should be replaced with a letter.
It's 32x9 with the hashtags so only the empty spaces are the actual field.
I don't know how to exclude the surrounding hashtags from the position and how to calculate the actual position from x and y.

   $position=($position_x)*($position_y);
   $field=substr_replace($field,'O',$position,1);
   echo("$field");

That's what I tried. I know that $position is wrong but I don't know how to fix it.
Is it even possible with the way I created the field or should I try it differently?
Thanks for your help in advance!

CodePudding user response：

You need to make sure your $field is correct. Your code has some syntax errors.

The trick is to calculate the coordinates.

increase x 1 for the left border
increase y 1 for the top border
the cols are 3, because of left border, right border and the newline
For the final position multiply the number of rows by number of columns plus x

$placeField = function (string $char, int $x, int $y): string {
    $cols = 30;
    $rows = 7;

    $topBottomFrame = str_repeat('#', $cols   2) . "\n";
    $centerFrame    = '#' . str_repeat(' ', $cols) . "#\n";
    $field          = $topBottomFrame . str_repeat($centerFrame, $rows) . $topBottomFrame;

    if ($x < 0 || $x >= $cols || $y < 0 || $y >= $rows) {
        return "Invalid coordinates\n";
    }

    $x  ;
    $y  ;

    return substr_replace($field, $char, $y * ($cols   3)   $x, 1);
};

echo $placeField("A", 0, 0);
echo $placeField("B", 29, 6);
echo $placeField("C", 15, 3);

Output

################################
#A                             #
#                              #
#                              #
#                              #
#                              #
#                              #
#                              #
################################
################################
#                              #
#                              #
#                              #
#                              #
#                              #
#                              #
#                             B#
################################
################################
#                              #
#                              #
#                              #
#               C              #
#                              #
#                              #
#                              #
################################