PHP Verification Code Implementation code simple example

Recently bored nothing to do, began to do some of the sharing of PHP, the code is relatively simple, but more practical.

This is written four years ago, a few lines of code to achieve four-bit random number of PHP verification code function.

code is as follows

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Session_Start (); Header (" Content-type:image/jpeg "); $img = Imagecreate (50,20); $white = imagecolorallocate ($img, 211,213,193); Imagefill ($img, 0,0, $white); <br <p>for ($i =0; $i <4; $i + +) { $r [$i] = rand (0,9); } $_session[' valid '] = Implode ("", $r); Writing here to the session can be done late validation for ($i =0 $i <4; $i + +) { if (rand (0,9)%2==0) { Imagechar ($img, 5, ($i + 1) *8,4, $r [$ I],imagecolorallocate ($img, Rand (0,150), Rand (0,150), Rand (0,150)); }else{ Imagechar ($img, 5, ($i + 1) *8,2, $r [$i],imagecolorallocate ($img, Rand (0,150), Rand (0,150), Rand (0,150))) ; } } imagejpeg ($img);