PHP verification code production (Network tree comment idea)_PHP tutorial

1, generate random numbers
Use a for loop to determine how many random numbers to generate.
Use a random function to generate random numbers within a range. For example, rand(1,15) generates a number between 1 and 15.
Use the 16-digit function to alphabetize the generated numbers. dechex(rand(1,15)).
Use the .= operation to save several numbers.
Put the generated random number into $_SESSION[variable]. Compare with user-submitted content in the future.
2. Create a picture
Use the picture creation function to determine the size of the created picture.
For example, $im = imagecreatetruecolor(100,30); where the coordinates 100 and 30 are based on the upper left corner of the web page as the origin, and $im is the image variable.
3. Set color
Use function to create background color. For example $bg = imagecolorallocate($im,0,0,0); where 0,0,0 are the three primary color numbers, $im is the image created above
Use the function to create the font color. For example, $te = imagecolorallocate($im,255,255,255);
4, write the characters in the upper left corner of the image
Use the function imagestring() to write the characters in the image. For example, imagestring($im,5,0,0,$rand,$te);$im is the image created above, 5 is the display mode, 0, 0
is the coordinate, $te is the font color
5, output image
Use the function header("Content-type:image/jpeg");imagejpeg($im); to output the image.
----------------------------------I am the gorgeous dividing line------- --------------------
1, enable the session function; for example, session_start();
2, write the form
3, verify the form submission The code data is compared with the above $_SESSION [variable]
and is verified to be correct.
If not equal, it is an error.

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