A PHP generated verification code implementation code_PHP tutorial

Generate verification code A PHP verification code generation code is implemented, and the session directory is customized, so that it is not the default session file saving path in php.ini. For example, session_save_path below can redefine the directory.

Generate verification code
A PHP tutorial generates verification code implementation code and customizes the session directory so that it is not the default session file saving path in php.ini, as shown below

session_save_path, the directory can be redefined.
*/
$sesssavepath = dirname(__file__)."/../data/sessions/";
if(is_writeable($sesssavepath) && is_readable($sesssavepath)){ session_save_path($sesssavepath); }
session_start();
$vstr = '';
for($i=0; $i<4; $i++) $vstr .= chr(mt_rand(65,90));
if(function_exists("imagecreate")){
$ntime = time();
if(empty($_session['verifycode_last']) || empty($_session['verifycode']) || ($ntime - $_session['verifycode_last'] > 5)){
$_session['verifycode'] = strtolower($vstr);
$_session['verifycode_last'] = $ntime;
}
$vstr = $_session['verifycode'];
$vstrlen = strlen($vstr);
$img = imagecreate(50,20);
imagecolorallocate($img, 255,255,255);
$line1 = imagecolorallocate($img,240,220,180);
$line2 = imagecolorallocate($img,250,250,170);
for($j=3;$j<=16;$j=$j+3){
imageline($img,2,$j,48,$j,$line1);
}
for($j=2;$j<52;$j=$j+(mt_rand(3,6))){
imageline($img,$j,2,$j-6,18,$line2);
}
$bordercolor = imagecolorallocate($img, 0x99,0x99,0x99);
imagerectangle($img, 0, 0, 49, 19, $bordercolor);
$fontcolor = imagecolorallocate($img, 48,61,50);
for($i=0;$i<$vstrlen;$i++){
$bc = mt_rand(0,1);
$vstr[$i] = strtoupper($vstr[$i]);
Imagestring($img, 5, $i*10+6, mt_rand(2,4), $vstr[$i], $fontcolor);
}

header("pragma:no-cachern");
header("cache-control:no-cachern");
header("expires:0rn");

if(function_exists("imagejpeg")){
header("content-type:image/jpegrn");
imagejpeg($img);
}else{
header("content-type:image/pngrn");
imagepng($img);
}
imagedestroy($img);
exit();
}