<?php     session_start();  // main  $vcodes = '';  //generate Number 4  srand((double) microtime() * 1000000);  for ($i = 0; $i < 4; $i++) {      $vcodes .= rand(1, 9);  }  $_SESSION['eifr_checkvcode'] = $vcodes;  if (function_exists('imagecreate')) {      //generate picture validation code      Header("Content-type: image/PNG");      $img = imagecreate(44, 18);      $bg  = ImageColorAllocate($img, 245, 245, 245);      imagefill($img, 0, 0, $bg); //background             //generate Number 4      for ($i = 0; $i < 4; $i++) {          $font = ImageColorAllocate($img, rand(100, 255), rand(0, 100), rand(100, 255));          $vnum = substr($vcodes, $i, 1);          imagestring($img, 5, 2 + $i * 10, 1, $vnum, $font);      }      //add interference      for ($i = 0; $i < 100; $i++) {          $randcolor = ImageColorallocate($img, rand(0, 255), rand(0, 255), rand(0, 255));          imagesetpixel($img, rand() % 70, rand() % 30, $randcolor);      }      ImagePNG($img);      ImageDestroy($img);  }  ?>