PHP functions (encryption and decryption, random strings, interception of string length, forced download, etc.)

function encryptdecrypt($key, $string, $decrypt){
 if($decrypt){
 $decrypted = rtrim(mcrypt_decrypt(mcrypt_rijndael_256, md5($key), base64_decode($string), mcrypt_mode_cbc, md5 (md5($key))), "12");
 return $decrypted;
 }else{
 $encrypted = base64_encode(mcrypt_encrypt(mcrypt_rijndael_256, md5($key), $string, mcrypt_mode_cbc, md5(md5($key ))));
 return $encrypted;
 }
}

Usage:

//The following is to encrypt and decrypt the string "helloweba welcomes you" respectively
//Encryption:
echo encryptdecrypt('password', 'helloweba welcomes you',0);
//Decryption:
 echo encryptdecrypt('password', 'z0jax4qmwcf+db5tnbp/xwdum84snrsxvvpxuaca4bk=',1);

2. PHP generates random string

When you need to generate a random name, temporary password and other strings, use the following function:

function generaterandomstring($length = 10) {
 $characters = '0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz';
 $randomstring = '';
 for ($i = 0; < $length; $i++) {
 $randomstring .= $characters[rand(0, strlen($characters) - 1)];
 }
 return $randomstring;
}

Usage:

echo generaterandomstring(20);

3. PHP gets the file extension (suffix) Quickly get the file extension or suffix.

function getextension($filename){
 $myext = substr($filename, strrpos($filename, '.'));
 return str_replace('.','',$myext);
}

How to use:

$filename = 'My Documents.doc';
echo getextension($filename);

4. PHP gets the file size and formats it Get the size of the file and convert it into kb, mb and other formats that are easy to read.

function formatsize($size) {
 $sizes = array(" bytes", " kb", " mb", " gb", " tb", " pb", " eb", " zb" , " yb");
 if ($size == 0) {
 return('n/a');
 } else {
 return (round($size/pow(1024, ($i = floor(log( $size, 1024)))), 2) . $sizes[$i]);
 }
}

Usage:

$thefile = filesize('test_file.mp3');
echo formatsize($thefile);

5. PHP replace tag characters Replace strings and template tags with specified content, function:

function stringparser($string,$replacer){
 $result = str_replace(array_keys($replacer), array_values($replacer),$string);
 return $result;
}

How to use:

$string = 'the {b}anchor text{/b} is the {b}actual word{/b} or words used {br}to describe the link {br}itself ';
$replace_array = array('{b}' => '','{/b}' => '','{br}' => '< ;br />');
echo stringparser($string,$replace_array);

6. PHP lists the directory file name List all files in a directory:

function listdirfiles($dirpath){
 if($dir = opendir($dirpath)){
 while(($file = readdir($dir))!== false){
 if(!is_dir ($dirpath.$file))
 {
 echo "filename: $file";
 }
 }
 }
}

How to use: listdirfiles('home/some_folder/');

7. Get the current page url with php The following function can get the url of the current page, whether it is http or https.

function curpageurl() {
 $pageurl = 'http';
 if (!empty($_server['https'])) {$pageurl .= "s";}
 $pageurl .= " ://";
 if ($_server["server_port"] != "80") {
 $pageurl .= $_server["server_name"].":".$_server["server_port"].$_server[ "request_uri"];
 } else {
 $pageurl .= $_server["server_name"].$_server["request_uri"];
 }
 return $pageurl;
}

How to use :

echo curpageurl();

8. PHP force download file If you do not want the browser to directly open a file, such as a pdf file, but to download the file directly, the following function can force the file to be downloaded. The application/octet-stream header type is used in the function.

function download($filename){
 if ((isset($filename))&&(file_exists($filename))){
 header("content-length: ".filesize($filename));
 header('content-type: application/octet-stream');
 header('content-disposition: attachment; filename="' . $filename . '"');
 readfile("$filename");
 } else {
 echo "looks like file does not exist!";
 }
}

Usage:

download('/down/test_45f73e852.zip');

9. PHP intercepts the string length When it is necessary to intercept the length of a string (including Chinese characters), such as how many characters cannot be exceeded in the title display, and the excess length is represented by..., the following function can meet your needs.

/*
 Chinese character interception function supported by both utf-8 and gb2312
 cut_str(string, interception length, start length, encoding);
 The encoding defaults to utf-8
 Start length Default is 0
*/
function cutstr($string, $sublen, $start = 0, $code = 'utf-8'){
 if($code == 'utf-8'){
 $pa = " /[x01-x7f]|[xc2-xdf][x80-xbf]|xe0[xa0-xbf][x80-xbf]|[xe1-xef][x80-xbf][x80-xbf]|xf0[x90- xbf][x80-xbf][x80-xbf]|[xf1-xf7][x80-xbf][x80-xbf][x80-xbf]/";
 preg_match_all($pa, $string, $t_string);< ;/p>
 if(count($t_string[0]) - $start > $sublen) return join('', array_slice($t_string[0], $start, $sublen))." ...";
 return join('', array_slice($t_string[0], $start, $sublen));
 }else{
 $start = $start*2;
 $sublen = $sublen*2;
 $strlen = strlen($string);
 $tmpstr = '';
 for($i=0; $i<$strlen; $i++){
 if($i> =$start && $i<($start+$sublen)){
 if(ord(substr($string, $i, 1))>129){
 $tmpstr.= substr($string, $i, 2 );
 }else{
 $tmpstr.= substr($string, $i, 1);
 }
 }
 if(ord(substr($string, $i, 1))>129) $i++;
 }
 if(strlen($tmpstr)<$strlen ) $tmpstr.= "...";
 return $tmpstr;
 }
}

How to use :

$str = "Loading images and page effects implemented by jquery plug-in";
echo cutstr($str,16);

10. Get the client’s real IP with php It is often necessary to use a database to record the user's IP and obtain the client's real IP:

//Get the user’s real ip
function getip() {
 if (getenv("http_client_ip") && strcasecmp(getenv("http_client_ip"), "unknown"))
 $ip = getenv("http_client_ip" ");
 else
 if (getenv("http_x_forwarded_for") && strcasecmp(getenv("http_x_forwarded_for"), "unknown"))
 $ip = getenv("http_x_forwarded_for");
 else
 if (getenv("remote_addr" ) && strcasecmp(getenv("remote_addr"), "unknown"))
 $ip = getenv("remote_addr");
 else
 if (isset ($_server['remote_addr']) && $_server['remote_addr'] && strcasecmp($_server['remote_addr'], "unknown"))
 $ip = $_server['remote_addr'];
 else
 $ip = "unknown";
 return ($ip);
}

How to use:

echo getip();

11. PHP prevents sql injection When querying the database, for security reasons, some illegal characters need to be filtered to prevent malicious SQL injection. Please take a look at the function:

function injcheck($sql_str) {
 $check = preg_match('/select|insert|update|delete|'|/*|*|../|./|union|into|load_file|outfile /', $sql_str);
 if ($check) {
 echo 'Illegal character! ! ';
 exit;
 } else {
 return $sql_str;
 }
}

The usage method is as follows:

function message($msgtitle,$message,$jumpurl){
 $str = '';
 $str .= '';
 $str .= ' ';
 $str .= '';
 $str .= 'Page prompt';
 $str .= '';
 $str .= '';
 $str .= '';
 $str .= ' ';
 $str .= ''.$msgtitle.'';
 $str .= '';
 $str .= ''.$ message.'';
 $str .= 'The system will automatically jump after 3 seconds Transfer, if you don’t want to wait, just click here Jump';
 $str .= "<script>settimeout('location .replace('".$jumpurl."')',2000)</script>";
 $str .= '

';

$str .= '';

$str .= '';

echo $str;

}

Copy code

Usage:

function changetimetype($seconds) {
 if ($seconds > 3600) {
 $hours = intval($seconds / 3600);
 $minutes = $seconds % 3600;
 $time = $hours . ":" . gmstrftime('%m:%s', $minutes);
 } else {
 $time = gmstrftime('%h:%m:%s', $seconds);
 }
 return $time ;
}

Usage:

$seconds = 3712; echo changetimetype($seconds);