PHP printing Yang Hui triangle small example

Example, PHP prints Yang Hui triangle.

/**
 * Print Yang Hui triangle:
 * 1
 * 1 1
 * 1 2 1
 * 1 3 3 1
 * 1 4 6 4 1
 * 1 5 10 10 5 1
 * 1 6 15 20 15 6 1
 *
*/
function yang_hui_san_jiao($n)
{
 $arr=array(1); //$arr records the previous line Element
 $return_html=''; //Define a variable to record the output html //The outer loop controls the number of lines for( $i=1;$i<=$n;$i++) { $return_html.=''; //The inner loop controls the number of changed elements for($j=1;$j<=$i;$j++) { //The first and last elements of the changed line are always 1 if($j==1 || $j==$i ) { $new_arr[$j]=1; // Define a new array $new_arr to record the elements of the current row, $return_html.=''; } $return_html.='









1';
 }
 else 
 {
 //Otherwise, this element is equal to the same subscript and subscript-1 of the previous row. The sum of the two elements
 $new_number=$arr[$j]+$arr[$j -1]; 
 $new_arr[$j]=$new_number; //Assign elements to the new array
 $return_html.=''.$new_number.'< /td>';
 }
 }
 $arr=$new_arr; //Assign the array of the current row to $arr and start a new cycle
< ;p> $return_html.='

';
 return $return_html;
}
//Call function to test Yang Hui triangle
echo yang_hui_san_jiao(10);
?>