PHP gets the md5 code of the uploaded file_PHP tutorial

Since it is necessary to determine whether the uploaded file has been modified, it is necessary to record the md5 value of the uploaded file. Here is the method of obtaining the md5 value of the file.

if(isset($_FILES['multimedia']) && $_FILES['multimedia']['error']==0)
{
	$file_name = $_FILES['multimedia']['name'];
	$size = getimagesize($_FILES['multimedia']['tmp_name']);
    $type = $_FILES['multimedia']['type'];
	$original = $_FILES['multimedia']['tmp_name'];
	$md5 = md5_file($original);
	echo $md5;
}

md5_file()

The md5_file() function calculates the MD5 hash of a file. The md5() function uses RSA data security, including the MD5 message digest algorithm. Returns the calculated MD5 hash on success, false on failure.

Syntax: md5(string,raw)

• Parameter string, required. Specifies the file to be calculated.
• Parameter charlist, optional. Specifies hexadecimal or binary output format: TRUE - raw 16-character binary format; FALSE - default. 32-character hexadecimal number.

<?php
$filename = "test.txt";
$md5file = md5_file($filename);
echo $md5file;
?>

Store the MD5 hash of the "test.txt" file:

<?php
$md5file = md5_file("test.txt");
file_put_contents("md5file.txt",$md5file);
?>

In this example, we will detect whether "test.txt" has been changed (i.e. whether the MD5 hash has been changed):

<?php
$md5file = file_get_contents("md5file.txt");
if (md5_file("test.txt") == $md5file)
{
	echo "The file is ok.";
}
else
{
	echo "The file has been changed.";
}
?>  

Output:

The file is ok.

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