嘿，我做了一个captcha，遇到了一些疯狂的问题。
我创建了一个shuffle变量并将其提供给会话，然后打开image.php
captcha.php
<?php
error_reporting(-1);
ini_set('display_errors', 1);
// Session start
SESSION_START();
// delet old CAPTCHA-Code from Session
unset( $_SESSION["captcha"] );
// the Array
$text[] = "2";
$text[] = "4";
$text[] = "5";
$text[] = "7";
$text[] = "8";
$text[] = "A";
$text[] = "B";
$text[] = "C";
$text[] = "D";
$text[] = "E";
$text[] = "F";
$text[] = "G";
$text[] = "H";
$text[] = "J";
$text[] = "K";
$text[] = "M";
$text[] = "N";
$text[] = "P";
$text[] = "Q";
$text[] = "R";
$text[] = "S";
$text[] = "T";
$text[] = "U";
$text[] = "V";
$text[] = "W";
$text[] = "X";
$text[] = "Y";
$text[] = "Z";
//mixup array
shuffle ( $text );
//getting the first 5 Charakters
$outputtext = array_slice ($text, 0, 5);
//give it to the session
$_SESSION["captcha"] = implode($outputtext);
session_write_close();
echo "Captcha ist: ".$_SESSION["captcha"];
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<img src="captchaimage.php" alt="" style="vertical-align: middle;">
</html>
captchaimage.php
<?php
error_reporting(-1);
ini_set('display_errors', 1);
SESSION_START();
Header ("Content-type: image/png");
$str = $_SESSION["captcha"];
$bild = ImageCreateFromPNG ("http://www.php.de/images/captcha.logo1.png");
$farbe_w = ImageColorAllocate ($bild, 255, 255, 255);
$farbe_b = ImageColorAllocate ($bild, 0, 0, 0);
ImageTTFText ($bild, 32, -30, 224, 112, $farbe_w, "arial.ttf",
$str[0]);
ImageTTFText ($bild, 32, -90, 288, 208, $farbe_w, "arial.ttf",
$str[1]);
ImageTTFText ($bild, 32, 0, 208, 336, $farbe_w, "arial.ttf",
$str[2]);
ImageTTFText ($bild, 32, 45, 128, 304, $farbe_w, "arial.ttf",
$str[3]);
ImageTTFText ($bild, 32, 99, 128, 192, $farbe_w, "arial.ttf",
$str[4]);
header( "Expires: Mon, 26 Jul 1997 05:00:00 GMT" );
header( "Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT" );
header( "Cache-Control: no-store, no-cache, must-revalidate" );
header( "Cache-Control: post-check=0, pre-check=0", false );
header( "Pragma: no-cache" );
ImagePng ($bild);
ImageDestroy ($bild);
?>
这很好，但如果我从captcha.php 中删除echo
此行：echo "Captcha ist: ".$_SESSION["captcha"];
我得到一个没有字符的图像，就像会话是空的一样，但如果会话真的是空的，就不会创建图像。
如果我在captcha.php中写了echo行，为什么captchaimage.php只得到正确的会话？
一个小测试：
稍微更改一下代码-不要调用captchaimage.php作为您的图像的源，而是尝试将您的captchaimage.php逻辑移动到captcha.php中，方法如下：
captcha.php
<?php
error_reporting(-1);
ini_set('display_errors', 1);
// Session start
SESSION_START();
// delet old CAPTCHA-Code from Session
unset( $_SESSION["captcha"] );
// the Array
$text = array("2", "4", "5", "7", "8", "A", "B", "C", "D", "E", /*...*/);
//mixup array
shuffle ( $text );
//getting the first 5 Charakters
$outputtext = array_slice ($text, 0, 5);
//give it to the session
$_SESSION["captcha"] = implode($outputtext);
$bild = ImageCreateFromPNG ("http://www.php.de/images/captcha.logo1.png");
$farbe_w = ImageColorAllocate ($bild, 255, 255, 255);
$farbe_b = ImageColorAllocate ($bild, 0, 0, 0);
ImageTTFText ($bild, 32, -30, 224, 112, $farbe_w, "arial.ttf", $str[0]);
ImageTTFText ($bild, 32, -90, 288, 208, $farbe_w, "arial.ttf", $str[1]);
ImageTTFText ($bild, 32, 0, 208, 336, $farbe_w, "arial.ttf", $str[2]);
ImageTTFText ($bild, 32, 45, 128, 304, $farbe_w, "arial.ttf", $str[3]);
ImageTTFText ($bild, 32, 99, 128, 192, $farbe_w, "arial.ttf", $str[4]);
ob_start();
ImagePng ($bild);
$image = ob_get_clean();
?>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<img src="data:image/png;base64,<?php echo base64_encode($image); ?>" alt="" style="vertical-align: middle;">
</html>
我希望这会奏效。