驗證碼一（驗證碼生成）

<?php
/**
* 根據手機好查詢密碼
* @return [type] [description]
*/
$code = "";
for ($i = 0; $i < 6; $i++) {
$code .= rand(0, 9);
}
//4位驗證碼也能夠用rand(1000,9999)直接生成
//將生成的驗證碼寫入session，備驗證時用
session_start();
$_SESSION["verify_num"] = $code;

//建立圖片，定義顏色值
header("Content-type: image/PNG");
$im = imagecreate(80, 30);
$black = imagecolorallocate($im, 0, 0, 0);
$gray = imagecolorallocate($im, 200, 200, 200);
$bgcolor = imagecolorallocate($im, 255, 255, 255);
//填充背景
imagefill($im, 0, 0, $gray);
//畫邊框
imagerectangle($im, 0, 0, 80-1, 30-1, $black);
//隨機繪製兩條虛線，起干擾做用
$style = array ($black,$black,$black,$black,$black,$gray,$gray,$gray,$gray,$gray);
imagesetstyle($im, $style);
$y1 = rand(0, 30);
$y2 = rand(0, 30);
$y3 = rand(0, 30);
$y4 = rand(0, 30);
imageline($im, 0, $y1, 80, $y3, IMG_COLOR_STYLED);
imageline($im, 0, $y2, 80, $y4, IMG_COLOR_STYLED);
//在畫布上隨機生成大量黑點，起干擾做用;
for ($i = 0; $i < 80; $i++) {
imagesetpixel($im, rand(0, 80), rand(0, 30), $black);
}
//將數字隨機顯示在畫布上,字符的水平間距和位置都按必定波動範圍隨機生成
$strx = rand(3, 8);
for ($i = 0; $i < 6; $i++) {
$strpos = rand(1, 6);
imagestring($im, 5, $strx, $strpos, substr($code, $i, 1), $black);
$strx += rand(8, 12);
}
imagepng($im);//輸出圖片
imagedestroy($im);//釋放圖片所佔內存

?>