PHP Verification Code Applet

Verification code function (personal understanding):

1. Reduce the pressure on the server (such as the 12306 verification code function);
2. Prevention of violent registration

Personal idea: generate N-bit random numbers in a-z,a-z,1-9 to form a new verification code.

A few small functions of generating verification code

1. Range ()//specify range output an array

A) such as: range (1,9)

1. Array_merge ()//merge Array

A) array_merge (array 1, Array 2 ...)

1. Array_rand (array, Number)

A) randomly remove several subscripts from the array to return an array

1. Shuffle (array)//will again disturb the elements in the array
2. Mt_rand (specify a range)//generate a better random number
3. For Example: Mt_rand (1,5)//generate an arbitrary number between 1-5

Generate code codes for verification codes

<?php

$arr 1=range (' a ', ' z ');//specify a range to output an array

$arr 2=range (' A ', ' Z ');

$arr 3=range (1,9);

$arr =array_merge ($arr 1, $arr 2, $arr 3); Merging arrays

$index = Array_rand ($arr, 5); Randomly take 5 numbers in $arr, The return value is the subscript of $arr

Shuffle ($index);

$code = ';//define An empty string to store the generated verification code with ' dot ' for stitching

foreach ($index as $key + $value) {//traversal Array

$code. = $arr [$value];//the values in the array according to the subscript

}

Var_dump ($code);

?>

Run results

Perfect: to add the verification code to the image of such a verification code to be realistic

Describe the approximate steps for image creation before you complete

Create an image

Method One: Create a true color image (empty Canvas)

Imagecreatetruecolor (width, Height)//create a true color image

Description

1. Width: breadth of canvas (pixels)
2. Height: the width of the canvas (pixels)
3. Return value is an image resource

Attention:

True Color image: Fill Color

Imagefill (image, x, y, color)//fill color for image resource

Description

1. Image//images Resource
2. x, y, The coordinate point of the fill (note: the color closest to this point is filled)

Color What color to fill with

For true color images: assigning colors

Imagecolorallocate (image, red, green, Blue)

Description

1. Image//images Resource
2. Red://color (0-255) or 0x (00-ff)//hexadecimal representation (0xff is 255)
3. Green//green Color (0-255)
4. Blue//blue Color (0-255)

Code demos for Imagefill and Imagecolorallocate

Effects when the canvas is not filled with color

Effects and code to fill the canvas with color

<?php

Creating an Image resource (blank Canvas) is displayed by default as Black

$image = Imagecreatetruecolor (300, 400);

1.image//image Resources

2.red://red color (0-255) or 0x (00-ff)//hexadecimal to indicate (0xff is 255)

3.green//green Color (0-255)

4.blue//blue Color (0-255)

$color = imagecolorallocate ($image, 255, 0, 0);

1.image//image Resources

2.x,y, filled coordinate point (note: the color closest to this point is filled)

3.color; What color to fill with

Imagefill ($image, 0, 0, $color);

Output image

Header (' Content-type:image/jpeg ');

Imagejpeg ($image);

Destroying image Resources

Imagedestroy ($image);

?>

Results

Output Image (jpeg for Example)

1. Output image to Browser

A) Header (' Content-type:image/jpeg '); Set the image to view by browsing

B) imagejpeg (image resources)

1. Output images by file

A) imagejpeg (image resource, ' image path ', image quality)//quality value 0-100

B) note:

Note: only the JPEG format has the quality of this parameter.

Destroying images

Imagedestroy ($image); Destroys the image and frees up memory Resources.

Note: Several image resources are currently generated and several are Destroyed.

The entire code of the Captcha:

<?php

Example: making text live in the middle of an image

Create an image resource (blank Canvas)

$image = Imagecreatetruecolor (100, 50);

$color = imagecolorallocate ($image, mt_rand (20,200), mt_rand (20,200), mt_rand (20,200));

Fill a color for an image resource

Imagefill ($image, 0, 0, $color);

Drawing an image

$font = 5;

The start of the verification code

$arr 1 = range (' a ', ' z ');

$arr 3 = range (' A ', ' Z ');

$arr 2 = Range (1,9);

Array_merge-merging one or more arrays

$arr = Array_merge ($arr 1, $arr 2, $arr 3);

$index = Array_rand ($arr, 5); Randomly identify 5 subscripts from the original array

$string = ";

foreach ($index as $value) {//$value two functions, which is the value in the $index and the subscript in the $arr

$string. = $arr [$value]; Will get the character to connect

}

End of verification code

Mt_rand-generate a better random number

echo Mt_rand (1,5);d ie;

Join Point Interference

$pointcolor = imagecolorallocate ($image, mt_rand (20,200), mt_rand (20,200), mt_rand (20,200));

Loop create 1000 interference points

For ($i =0; $i <1000; $i + +) {

Imagesetpixel ($image, mt_rand (0,imagesx ($image)), mt_rand (0,imagesy ($image)), $pointcolor);

}

Interference in line join

$lintecolor = imagecolorallocate ($image, mt_rand (20,200), mt_rand (20,200), mt_rand (20,200));

Loop Create 50 Line disturbances

For ($i =0; $i <50; $i + +) {

Imageline ($image, mt_rand (0,imagesx ($image)), mt_rand (0,imagesy ($image)), mt_rand (0,imagesx ($image)), mt_rand (0, Imagesy ($image)), $lintecolor);

}

Width of one character imagefontwidth ($font)

Number of strings: strlen (string)

The width of a character * number of strings

All string widths and = width of one character * number of strings

$x = (width of Canvas-all string widths AND)/2

$x = (imagesx ($image)-imagefontwidth ($font) *strlen ($string))/2;

$y = (height of the canvas-the height of the character)/2;

Height of character: imagefontheight ($font)

$y = (imagesy ($image)-imagefontheight ($font))/2;

$stringcolor = imagecolorallocate ($image, mt_rand (20,200), mt_rand (20,200), mt_rand (20,200));

Imagestring ($image, $font, $x, $y, $string, $stringcolor);

Output image

Header (' Content-type:image/jpeg '); Set the image to view by browsing

Imagejpeg ($image, ", 100); Exporting an image resource

Destroying image Resources

Imagedestroy ($image); Destroying images

Understand some of the functions in the code

Join the point of interference

Imagesetpixel (image, x, y, color)

Description: x, y coordinates of a point

Join the line of interference

Imageline (image, x1, y1, x2, y2, color)

Description: X1,y1 is an endpoint coordinate of the line; X2,y2 is the coordinate of the other port of the line; Draw a line from two points

Let the captcha reside in the center of the image

1. Imagefontheight (font) Gets the height of the font:
2. Imagefontwidth (font) Gets the width of the font:
3. Strlen (string)//gets The length of the string
4. Imagesx (image)//get the width of the canvas
5. Imagesy (image)//get The height of the canvas

Last Run result

Perfect again (together with HTML Code)

HTML code

<! DOCTYPE html>

<meta charset= "UTF-8" >

<title>Document</title>

<body>

<form name= ' frm ' method= ' post ' action= ' >

<table width= "30%" border= "2" align= "center" rules= "all" cellpadding= "ten" >

<tr>

<th colspan= "2" > Please enter information </th>

</tr>

<tr>

<th> name:</th>

<th><input type= "text" name= "username" ></input></th>

</tr>

<tr>

<th> password:</th>

<th><input type= "password" name= "userpwd" ></input></th>

</tr>

<tr> 555556

<th> Verification Code </th>

<th><input type = ' text ' name = ' Checkcode ' ></input></th>

</tr>

<tr>

<th colspan= "2" ><input type= "submit" name= "submit" value= "submission" ></input></th>

</tr>

</table>

</form>

</body>

Understand

Final results

PHP Verification Code Applet