我有一个html表单，它发布到post_form.php进行处理。当我试图提交联系表格时，我收到了这个错误：
Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at C:'wamp'www'advanced-dynamic-php-form'form-files'post_form.php:1) in C:'wamp'www'advanced-dynamic-php-form'form-files'post_form.php on line 2
Call Stack
# Time Memory Function Location
1 0.0011 283424 {main}( ) ..'post_form.php:0
2 0.0011 284240 session_start ( ) ..'post_form.php:2
我已经检查了session_start（）；出现在打开php标记后的页面上。我还检查了php.ini文件，以确保session.auto_start=0。这是php页面：
<?php
session_start();
isset($_FILES['contact_form']);
$body = "";
if(isset($_POST["submit"])){
if(isset($_POST["captcha"])&&$_POST["captcha"]!=""&&$_SESSION["code"]==$_POST["captcha"])
{
$to = "info@lexomatic.com";
$subject = "Contact";
$name = $_POST['name'];
$email = $_POST['email'];
$phone = $_POST['phone'];
$address = $_POST['address'];
$message = $_POST['message'];
$total_lines = $_POST['total_lines'];
$dirname = str_replace ("@","",$email);
$allowed = array('jpg', 'png', 'gif', 'doc', 'docx', 'pdf', 'xls', 'xlsx', 'zip', 'rar', 'JPG', 'PNG', 'GIF', 'DOC', 'DOCX', 'PDF', 'XLS', 'XLSX', 'ZIP', 'RAR');
$i=0;
$num_of_att = 0;
$error_ext = 0;
$error_size = 0;
$upload_error =0;
$target1 = "";
$target2 = "";
$target3 = "";
$img_url1 = "";
$img_url2 = "";
$img_url3 = "";
// File Attachment Function
for ($file_num=1; $file_num<=3; $file_num++){
${'ok'.$file_num} = 0;
$input_name = "file".$file_num;
if(!empty($_FILES[$input_name]["name"] )){
${'target'.$file_num} = $_SERVER['DOCUMENT_ROOT'] . '/form-files/uploads/'.$dirname .'/'. $_FILES[$input_name]["name"];
${'img_url'.$file_num} = 'http://YOURSITEURL.COM/form-files/uploads/'.$dirname .'/'. $_FILES[$input_name]["name"];
$file_ext = $_FILES[$input_name]["name"];
$ext = end(explode(".", $file_ext));
//$file_ext = new SplFileInfo(${'target'.$file_num});
//$ext = $file_ext->getExtension();
if(!in_array($ext,$allowed) ) {
$error_ext++;
$error_message = "<div style='width: 250px; color: red; font-family: Arial; font-weight: normal; font-size:12px'>Extensions " .$ext. " are not allowed</div>";
} elseif(($_FILES[$input_name]['size'] > 2097152) || ($_FILES[$input_name]['size'] == 0)){
$error_size++;
$error_message = "<div style='margin-left:15px; width: 250px; color: red; font-family: Arial; font-weight: normal; font-size:12px'>File " .$input_name. " exceeds max file size</div>";
}else{
${'ok'.$file_num} = 1;
$num_of_att++;
${'cur_temp_name'.$file_num} = $_FILES[$input_name]["tmp_name"];
} //close if
}//close if
}//close for
// File attachment check
$counter = 0;
if(($num_of_att>0) && ($error_size==0) && ($error_ext==0)){
if (!file_exists("uploads/".$dirname)) {
mkdir("uploads/$dirname", 0777, true);
}
if($ok1 == 1){
if(move_uploaded_file($cur_temp_name1, $target1)){
$counter++;
}else{
$upload_error++;
}
}
if($ok2 == 1){
if(move_uploaded_file($cur_temp_name2, $target2)){
$counter++;
}else{
$upload_error++;
}
}
if($ok3 == 1){
if(move_uploaded_file($cur_temp_name3, $target3)){
$counter++;
}else{
$upload_error++;
}
}
}
//////////////////////// Create Email Body ////////////////////////////////
// if(($num_of_att==0) && ($error_size==0) && ($error_ext==0)){
/*while (list($key,$value) = each($_POST)){
$body .= $key.": " .$value."'n";
}*/
if(($upload_error == 0) && ($error_size==0) && ($error_ext==0)){
$body .= "Name: ".$name."'n";
$body .= "Email: ".$email."'n";
$body .= "Phone: ".$phone ."'n";
$body .= "Address: ".$address."'n";
$body .= "Message: ".$message."'n'n";
for($i=1; $i<=20; $i++){
$dynamicentryvaluefirst = 'dynamicentryvaluefirst'.$i;
$dynamicentryvaluesecond = 'dynamicentryvaluesecond'.$i;
$dynamicentryvaluethird = 'dynamicentryvaluethird'.$i;
$dynamicentryvaluefourth = 'dynamicentryvaluefourth'.$i;
$dynamicentryvaluefifth = 'dynamicentryvaluefifth'.$i;
if (isset($_POST[$dynamicentryvaluefirst])){
$cur_dynamicentryvaluefirst = $_POST[$dynamicentryvaluefirst];
}else{
$cur_dynamicentryvaluefirst ="";
}
if (isset($_POST[$dynamicentryvaluesecond])){
$cur_dynamicentryvaluesecond = $_POST[$dynamicentryvaluesecond];
}else{
$cur_dynamicentryvaluesecond ="";
}
if (isset($_POST[$dynamicentryvaluethird])){
$cur_dynamicentryvaluethird = $_POST[$dynamicentryvaluethird];
}else{
$cur_dynamicentryvaluethird ="";
}
if (isset($_POST[$dynamicentryvaluefourth])){
$cur_dynamicentryvaluefourth = $_POST[$dynamicentryvaluefourth];
}else{
$cur_dynamicentryvaluefourth ="";
}
if (isset($_POST[$dynamicentryvaluefifth])){
$cur_dynamicentryvaluefifth = $_POST[$dynamicentryvaluefifth];
}else{
$cur_dynamicentryvaluefifth ="";
}
${'line'.$i} = $cur_dynamicentryvaluefirst . " | " . $cur_dynamicentryvaluesecond . " | " . $cur_dynamicentryvaluethird . " | " . $cur_dynamicentryvaluefourth . " | " . $cur_dynamicentryvaluefifth;
if(${'line'.$i} == (" | | | | ")){
}else{
$body .= "Line".$i.": ".(${'line'.$i})."'n";
}
}
$body .= "'n"."File 1: ".$img_url1."'n";
$body .= "File 2: ".$img_url2."'n";
$body .= "File 3: ".$img_url3."'n";
$sent = mail($to, $subject, $body);
//echo "Body----------------------"."<br/>".$body;
echo "<div style='position: relative; top: -10px; margin-left:15px; width: 250px; color: green; font-family: Arial; font-weight: normal; font-size:12px'><img src='tick-icon.png' width='70px' /><div id='message_result'>The form submitted successfully.</div></div>";
}else{
echo "<div style='margin-left:15px; width: 250px; color: red; font-family: Arial; font-weight: normal; font-size:12px'><img src='delete-icon.png' width='70px' /><div id='message_result'>An error occured while uploading the file(s).<br/>". $error_message . "</div></div>";
}
}else{
echo "<div style='margin-left:15px; width: 250px; color: red; font-family: Arial; font-weight: normal; font-size:12px'><img src='delete-icon.png' width='70px' /><div id='message_result'>Wrong security code number.</div></div>"; // invalid code
}
}else{
echo "<div style='margin-left:15px; width: 250px; color: red; font-family: Arial; font-weight: normal; font-size:12px'><img src='delete-icon.png' width='70px' /><div id='message_result'>An error occured. <br/>Please check file sizes and types & try again.</div></div>";
session_destroy();
}
?>
如有任何协助，我们将不胜感激。
假设<?php ...和... ?>之间的所有内容都将被删除，那么剩下的内容将以html的形式"输出"到浏览器。
这总是一个p-i--a，因为php标记前后的换行符、空格、退格等不可见字符，甚至它们之间的字符都可能会打乱输出。
像这样的东西
<?php
/**
* some comments
*/
?>
<?php
...
你需要几个小时才能找到。这里：?>和第二个<?php 之间的两个（！）nl