php如何创建验证码

/**
* 生成验证码
* @param int $type
* @param int $length
* @return string
*/
function buildRandomString($type=1,$length=4){
if ($type == 1) {
$chars = join ( "", range ( 0, 9 ) );
} elseif ($type == 2) {
$chars = join ( "", array_merge ( range ( "a", "z" ), range ( "A", "Z" ) ) );
} elseif ($type == 3) {
$chars = join ( "", array_merge ( range ( "a", "z" ), range ( "A", "Z" ), range ( 0, 9 ) ) );
}
if ($length > strlen ( $chars )) {
exit ( "字符串长度不够" );
}
$chars = str_shuffle ( $chars );
return substr ( $chars, 0, $length );
}

require_once 'string.func.php';

//通过GD库做验证码

function verifyImage($type=1,$length=4,$pixel=0,$line=0,$sess_name = "verify"){
//创建画布
$width = 80;
$height = 28;
$image = imagecreatetruecolor ( $width, $height );
$white = imagecolorallocate ( $image, 255, 255, 255 );
$black = imagecolorallocate ( $image, 0, 0, 0 );
//用填充矩形填充画布
imagefilledrectangle ( $image, 1, 1, $width - 2, $height - 2, $white );
$chars = buildRandomString ( $type, $length );
$_SESSION [$sess_name] = $chars;
//这里需要创建一个文件夹来存放字体
$fontfiles = array ("LHANDW.TTF","LSANS.TTF","LTYPE.TTF");

for($i = 0; $i < $length; $i ++) {
$size = mt_rand ( 14, 18 );
$angle = mt_rand ( - 15, 15 );
$x = 5 + $i * $size;
$y = mt_rand ( 20, 26 );
$fontfile = "../fonts/" . $fontfiles [mt_rand ( 0, count ( $fontfiles ) - 1 )];
$color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
$text = substr ( $chars, $i, 1 );
imagettftext ( $image, $size, $angle, $x, $y, $color, $fontfile, $text );
}
//创建模糊点
if ($pixel) {
for($i = 0; $i < 50; $i ++) {
imagesetpixel ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $black );
}
}
//创建模糊线
if ($line) {
for($i = 1; $i < $line; $i ++) {
$color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
imageline ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $color );
}
}
//展示图片
header ( "content-type:image/gif" );
imagegif ( $image );
imagedestroy ( $image );
}