Find the highest prime number in a given range

Question

I need to find the highest prime number in a given range.
Here is my code which works for 0-100 but if I give 0-125 it is showing prime number as 125.

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Answer 1

Yup the problem is algorithmic...

1) You'll need to check up till sqrt($b) i.e. 11 in this case

2) The $flag logic is kinda messed up, no use changing the flag then breaking out right after...

=0;$i--)
        {

            if($i%2!=0)
            {
                    for($b=3;$b<=$sq;$b++)
                    {
                            if($i%$b!=0)
                            {
                                $flag=1;
                            }
                            elseif($i%$b==0)
                            {
                                $flag=0;
                                break;
                            }
                    }
            if($flag==1){ 
                echo('highest prime number is '.$i);  
                break;
            }
        }
    }
?>