is_prime

<?php  //turn error reporting on  error_reporting( E_ERROR | E_WARNING | E_PARSE | E_NOTICE );  //Determines if the given integer is prime  function is_prime( $integer )  {    //Define variable used for counting    $divisor = 1;    //Cannot divide by zero    if( $integer == 0 )    {      return( 0 );    }    while( $divisor <= $integer )    {      //Do the math, division      $quotient = $integer / $divisor;      if( $divisor != 1 && $divisor != $integer && gettype( $quotient ) == 'integer' )      {        //The integer is not aprime number        return( 0 );      }      else if( $divisor == 1 && $integer == 1 )      {        return( 0 );      }      //Display each equation      //echo '      <li><em>' . $integer . ' / ' . $divisor . ' = ' . $quotient . '</em></li>';      $divisor++;    }    //The integer is a prime number    return( 1 );  }  //Shorthand reference for form data  $integer = $_POST[ 'integer' ];  if( isset( $integer ) )  {    if( is_prime( $integer ) )    {      $result = 'The integer ' . $integer . ' is a prime number.';    }    else    {      $result = 'The integer ' . $integer . ' is <b>not</b> a prime number.';    }  }  ?><html>  <head>    <title>Prime</title>  </head>  <body>    <form action="http://localhost/math/prime.php" method="post">    <ul style="list-style-type: none;">      <li><?php echo $result; ?></li>      <li><input type="text" name="integer" width="10" /></li>      <li><input type="submit" value="submit" /></li>    </ul>    </form>    <ul style="list-style-type: none;"><?php  for( $i = 1; $i <= 30; $i++ )  {    //Determine if the current number is from or not    if( is_prime( $i ) )    {      $result = 'The integer ' . $i . ' is a prime number.';    //Add result to list    echo '      <li>' . $result . '</li>' . "\n";    }    else    {      $result = 'The integer ' . $i . ' is <b>not</b> a prime number.';    }      }?>    </ul>  </body></html>