How to compare form data in php - php

Question

HTML/PHP:
<form method="post" name="contact" id="frmContact" action="sM.php">
<img id="main-img" src="theimage/img1.png" name="imageval" />
<div style="clear: both; padding: 10px 0 0 0; overflow: hidden;">
Please enter the number(s) from the image above: <input type="text" id="tNum" placeholder="Enter Number(s)" name="numval" />
</div>
<input type="submit" value="Send" id="submit" name="submit" class="submit_btn" />
</form>
PHP:
$arrImg = array("img1", "img2", "img3", "img4", "img5", "img6");
$arrImgText = array("56", "342", "34534", "12", "444", "652");
$imgval = trim(strip_tags(stripslashes($_POST['imageval']))); //get the image source that was displayed in the form
$numval = trim(strip_tags(stripslashes($_POST['numval']))); //get the number that the user entered
//if ({arrImg[imgval] == arrImgText[numval]}) {
//do something;
//}
The image that is displayed in the form has some numbers. When the user hit send, I would like to compare the number that was entered that was displayed in the image and compare.
How can I do that.

Answer 1

In your form, create hidden input:
<input type="hidden" name="imageval" value="img1" />
In your PHP file you can have now two $_POST variables:
$secretImg = $_POST['imageval'];
$token = $_POST['numval'];
Now you need to find key of image:
$imgKey = array_search($secretImg, $arrImg);
Using the key value, check the proper token:
if ($arrImgText[$imgKey] === $token) {
// Token is valid
}

Answer 2

You can't pass images because it is not an input element, what you could do is use a hidden input element instead:
<form method="post" name="contact" id="frmContact" action="sM.php">
<img id="main-img" src="theimage/img1.png" />
<input type="hidden" val="img1" name="imageval" /> <!-- THIS IS THE HIDDEN INPUT ELEMENT THAT WILL BE SUBMITTED -->
<div style="clear: both; padding: 10px 0 0 0; overflow: hidden;">
Please enter the number(s) from the image above: <input type="text" id="tNum" placeholder="Enter Number(s)" name="numval" />
</div>
<input type="submit" value="Send" id="submit" name="submit" class="submit_btn" />
</form>
In order to search the image value in the array using PHP, you can use in_array:
if( in_array( $_POST['imageval'], $arrImgText ) {
echo "Image found";
}
Edit: To get the specific index, use the example in #GrzegorzGajda'a answer