Use PHP to implement a simple version of file upload function (super detailed explanation)

1. PHP simplified version of image upload (without various verifications)

<form action="" enctype="multipart/form-data" method="post" >
请选择需要上传的文件：<input type="file" name="upfile" /><br>
<input type="submit" value="上传" />
</form>

First of all, we need to add enctype="multipart/form-data" to the form form to indicate that there will be images sent in the declaration form. action=”” means the current page is submitted, method=”post” The transmission method is post

<?php
if(is_uploaded_file($_FILES[&#39;upfile&#39;][&#39;tmp_name&#39;])){
$upfile=$_FILES["upfile"];
$name=$upfile[&#39;name&#39;];
$tmp_name=$upfile["tmp_name"];//上传文件的临时存放路径
move_uploaded_file($tmp_name,&#39;up/&#39;.$name);
echo "上传成功";
}
else{
    echo "您还没有上传文件";
}
?>

Keyword summary

is_uploaded_file means to verify whether the file is uploaded through HTTP POST, and the conditions are met. Normal upload

$_FILES['upfile']['tmp_name']) means getting the local location of the currently transferred image

move_uploaded_file($tmp_name,'up/'.$name); , this method has two parameters, the first is the file name of the uploaded file, the second is to move the file to this location

2. Writing and reading files

First Introduction to writing:

     $myfile = fopen("comment/" .time().'-'. rand(0, 1000) . ".comment", "a") or die("Unable to open file!");
        $txt = time().&#39;<br />&#39;;
        fwrite($myfile, $txt);
        fclose($myfile);

The role of the fopen function is to write data. The first parameter is the specific path to the file, and the second parameter means to put the read data into the file, where the file The name is composed of a timestamp plus a random number, and the suffix is ​​comment. A means opening in writing mode and pointing the file pointer to the end of the file. If the file does not exist, try to create it, or die means the execution fails, and execute Unable to open file! (unable to open the file).

The second sentence means data. The data can be transmitted by post or get, whatever you want

The third sentence fwrite means writing to the file. The first parameter is the location of the written file. , the second one is the data to be written

The fourth sentence means closing the file, indicating that the writing is completed, and this execution is completed

$list = glob("comment/*.comment");
rsort($list);
for ($i = 0; count($list) > $i; $i++) {
    $file_path = $list[$i];
    if (file_exists($file_path)) {
        $fp = fopen($file_path, "r");
        $str = fread($fp, filesize($file_path));//指定读取大小，这里把整个文件内容读取出来
        echo $str = str_replace("\r\n", "<br />", $str);
    }
}

Read in the introduction:

The key statement is

The first sentence: First use (glob) to find the file that needs to be read. If there are many files that meet the conditions, then they will be saved in an array, and traversal is used when reading. Arrays are enough

Second sentence: rsort is descending order, mainly to meet the sorting under specific conditions, such as according to release time

Third sentence: Because it can be sorted through var_dump, print, etc. We know that glob saves paths in the form of an array, so we use count to calculate the total, and then traverse one by one to get the file path that needs to be read

The fourth sentence: $file_path gets the file path

Fifth sentence: file_exists determines whether the file exists

Sixth sentence: fopen reads the file and opens it in read-only mode

Seventh sentence: fread first parameter Indicates what is read, and the second one indicates the size of the file read, which here also indicates how much is read.

The eighth sentence: str_replace replacement function means replacing all \r\ in $str Replace n with br (indicates line break, replace it with line break in the web page)

The above is the detailed content of Use PHP to implement a simple version of file upload function (super detailed explanation). For more information, please follow other related articles on the PHP Chinese website!