A very practical summary of common PHP functions - encryption and decryption, string operations, file operations, SQL injection and other functions

The examples in this article summarize some functions commonly used in PHP application development. These functions include character operations, file operations and other operations. They are shared with everyone. refer to. The details are as follows:

1. PHP encryption and decryption

PHP encryption and decryption functions can be used to encrypt some useful strings and store them in the database, and to reversibly decrypt the strings. This function uses base64 and MD5 encrypt and decrypt.

The code is as follows

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; 
    } 
}

The usage method is as follows:

//以下是将字符串“Helloweba欢迎您”分别加密和解密 
//加密： 
echo encryptDecrypt('password', 'Helloweba欢迎您',0); 
//解密： 
echo encryptDecrypt('password', 'z0JAx4qMwcF+db5TNbp/xwdUM84snRsXvvpXuaCa4Bk=',1);

2. PHP generates a random string

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

The code is as follows

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

The usage method is as follows:

echo generateRandomString(20);

3. PHP obtains the file extension (suffix)

The following function can quickly obtain the file extension or suffix.

The code is as follows

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

The usage method is as follows:

$filename = '我的文档.doc'; 
echo getExtension($filename);

4. PHP gets the file size and formats it

The functions used below can obtain the size of the file and convert it into KB, MB and other formats that are easy to read.

The code is as follows

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]);  
    } 
}

The usage method is as follows:

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

5. PHP replaces tag characters

Sometimes we need to replace strings and template tags with specified content. We can use the following function:

The code is as follows

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

The usage method is as follows:

$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}' => '
'); 
 
echo stringParser($string,$replace_array);

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