The idea and implementation of php generating SessionID and image verification code

A verification code is required for backend login, and SessionID is required for user tracking in the frontend. Of course, the default PHP will have a SessionID after opening the Session, but I need my own and can be stored in the database, then I I gave it a try and constructed the following function.

/****** Generate Session ID ******/
The basic idea is to obtain the current microsecond time, then generate a random number, add the random number to the current time and encrypt it, and finally intercept the required length
/*
Function name: create_sess_id()
Function function: Generate a random session ID
Parameter: $len: The length of the session string is required, the default is 32 bits, not less than 16 bits
Return value: Return the session ID
Function heiyeluren
*/
function create_sess_id($len=32)
{
// Verify whether the submitted length is legal
if( !is_numeric($len) || ($len>32) || ($len< 16)) { return; }
// Get the microseconds of the current time
list($u, $s) = explode(' ', microtime());
$time = (float)$u (float)$s ;
// Generate a random number
$rand_num = rand(100000, 999999);
$rand_num = rand($rand_num, $time);
mt_srand($rand_num);
$rand_num = mt_rand();
// Generate SessionID
$sess_id = md5( md5($time). md5($rand_num) );
//Intercept the SessionID of the specified required length
$sess_id = substr($sess_id, 0, $len);
return $sess_id;
}


/****** Generate verification code ******/
Idea: This idea is relatively simple, because considering the uniqueness and randomness, our verification code only needs to intercept a string from the Session ID, because our SessionID is Uniquely thought out.

/*
Function name: create_check_code()
Function function: Generate a random check code
Parameter: $len: The length of the check code required, please not be longer than 16 digits, the default is 4 digits
Return value : Returns the check code of the specified length
function heiyeluren
*/
function create_check_code($len=4)
{
if ( !is_numeric($len) || ($len>6) || ($len<1) ) { return; }

$check_code = substr(create_sess_id(), 16, $len );
return strtoupper($check_code);
}


/****** Picture of generating verification code ******/

These are some simple ones PHP image programming stuff, I'm making images and it's simple.

/*
Function name: create_check_image()
Function function: Generate a check code image
Parameter: $check_code: Check code string, usually obtained by the create_check_code() function
Return value: Return the image
Function heiyeluren
*/
function create_check_image( $check_code )
{
// Generate an image
$im = imagecreate(65,22);
$black = ImageColorAllocate($im, 0,0,0); // Background Color
$white = ImageColorAllocate($im, 255,255,255); // Foreground color
$gray = ImageColorAllocate($im, 200,200,200);
imagefill($im,68,30,$gray);

// Change four digits The integer verification code is drawn into the image
imagestring($im, 5, 8, 3, $check_code, $white);
// Add interference pixels
for($i=0;$i<200;$i )
{
$randcolor = ImageColorallocate($im,rand(0,255),rand(0,255),rand(0,255));
imagesetpixel($im, rand()p , rand()0 , $randcolor);
}
// Output image
Header("Content-type: image/PNG");
ImagePNG($im);
ImageDestroy($im);
}

Here we should note that when referencing the create_check_image() function, it must be in a In a separate file, because the output format when outputting the file header is an image format, mixed with other content, the image will not be displayed. In addition, you can change the image generation function. For example, if you want to change the color, then you change the generation positions of the foreground color and background color, then the colors will be different. At the same time, you also need to change the color of the check code. Change it, otherwise the background and check code will be black and will not be displayed. Please indicate the source when reprinting: The idea and implementation of php generating SessionID and image verification code