It looks nice. Can you please make me understand how it works

For example

 function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);}

Output

     *     
     *     
     *     
     *     
     *     
***********
     *     
     *     
     *     
     *  

Sandbox

Let me write it in a way that is easier to see

$n = 5;
$row_len = $n*2+1;
$output = '';
$default = str_pad('*',$row_len,' ',2); //is = "     *     "

for($i=0;$i<$row_len;++$i){
    if($i==$n){
        $output .= str_repeat('*',$row_len);//is = "***********"
    }else{
        $output .= $default;
    }
}

echo chunk_split($output, $row_len);  //is = "     *          *     ***********"

Sandbox

Basically we can create the " * " row by using string pad. Because we can pad spaces on both sides of a * up to the length of a row ($n*2)+1.

Then the center row, is just * so we can use string repeat to the length of the row for that line.

Last we take our big huge line of spaces and * and split it into chunks (\n) on the length of our row we want.

It looks nice. Can you please make me understand how it works

For example

 function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);}

Output

     *     
     *     
     *     
     *     
     *     
***********
     *     
     *     
     *     
     *  

Sandbox

Let me write it in a way that is easier to see

$n = 5;
$row_len = $n*2+1;
$output = '';
//pad $n spaces on each side of *
$default = str_pad('*',$row_len,' ',STR_PAD_BOTH); //is = "     *     "

//loop once for each vertical row (same as width)
for($i=0;$i<$row_len;++$i){
    if($i==$n){
        //do the center line all *'s
        $output .= str_repeat('*',$row_len);//is = "***********"
    }else{
        //use the default line from above
        $output .= $default;
    }
}

//now we have a single line that is the length squared so we can chunk it
//into equal parts, to make a square
echo chunk_split($output, $row_len);  //is = "     *          *     ***********"

Sandbox

Basically we can create the " * " row by using string pad. Because we can pad spaces on both sides of a * up to the length of a row ($n*2)+1.

Then the center row, is just * so we can use string repeat to the length of the row for that line.

Last we take our big huge line of spaces and * and split it into chunks (\n) on the length of our row we want.

It looks nice. Can you please make me understand how it works

For example

 function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);}

Output

     *     
     *     
     *     
     *     
     *     
***********
     *     
     *     
     *     
     *  

Sandbox

Let me write it in a way that is easier to see

$n = 5;
$row_len = $n*2+1;
$output = '';
$default = str_pad('*',$row_len,' ',2); //"     *     "

for($i=0;$i<$row_len;++$i){
    if($i==$n){
        $output .= str_repeat('*',$row_len);//"***********"
    }else{
        $output .= $default;
    }
}

echo chunk_split($output, $row_len);  //"     *          *     ***********"

Sandbox

It looks nice. Can you please make me understand how it works

For example

 function f($n){$s='';$b=str_pad('*',($m=$n*2+1),' ',2);for($i=0;$i<$m;++$i)$s.=($i==$n)?str_repeat('*',$m):$b;return chunk_split($s, $m);}

Output

     *     
     *     
     *     
     *     
     *     
***********
     *     
     *     
     *     
     *  

Sandbox

Let me write it in a way that is easier to see

$n = 5;
$row_len = $n*2+1;
$output = '';
$default = str_pad('*',$row_len,' ',2); //is = "     *     "

for($i=0;$i<$row_len;++$i){
    if($i==$n){
        $output .= str_repeat('*',$row_len);//is = "***********"
    }else{
        $output .= $default;
    }
}

echo chunk_split($output, $row_len);  //is = "     *          *     ***********"

Sandbox

Basically we can create the " * " row by using string pad. Because we can pad spaces on both sides of a * up to the length of a row ($n*2)+1.

Then the center row, is just * so we can use string repeat to the length of the row for that line.

Last we take our big huge line of spaces and * and split it into chunks (\n) on the length of our row we want.