How can i use custom function to validate post data in php - php

Question

I want to validate my form post using function and then insert it into database.
I have been able to do that without putting it into function but when i put it into a function it inserts without validating the input fields.
Thanks ;)
Here is my code:
<?php
function validate_post(){
global $link;
if (isset($_POST['submit'])) {
$error = array();
if (!isset($_POST['cat_title']) || empty($_POST['cat_title'])) {
$error[] = "field cannot be empty";
} else {
//check if a name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z]*$/", $_POST['cat_title'])) {
$cat_err = "Only letters and whitespace allowed";
}
}
//if no errors found
if (empty($error) && empty($cat_err)) {
$cat_title = htmlentities($_POST['cat_title']);
$sql = "INSERT INTO categories(cat_title)VALUES('$cat_title')";
$insert = mysqli_query($link, $sql);
confirm_query($insert);
if (mysqli_affected_rows($link) == 1) {
$post_info = "Category has been added";
redirect("categories.php");
} else {
$post_info = "Adding category failed";
}
} else {
$post_info = "Field cannot be empty";
}
}
}
?>
<?php validate_post(); ?><!-- call validate_post function-->
<!-- ADD CATEGORY FORM -->
<form action="" method="post">
<?php
if(isset($post_info))echo $post_info."<br>";
if(isset($cat_err))echo $cat_err."\n" ?>
<div class="form-group">
<label for="cat_tile">Categories</label>
<input type="text" class="form-control" name="cat_title" id="cat_tile"/>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="+ Add Category" name="submit" >
</div>
</form>

Answer 1

You can pass your post data by reference to a function like this:
function checkFormValue(&$inputData) {
if (isset($inputData) && !empty($inputData)) {
return $inputData;
}
return "";
}
Call this function on $_POST data to validate it:
$catTitle = checkFormValue($_POST["cat_title"]);
var_dump($catTitle);
If it fails to validate than it will return empty string. Using this function you can check isset and for !empty many of your form fields.

Answer 2

below code will help you ..
<?php
function validate_post(){
global $link;
if (isset($_POST['submit'])) {
$cat_err = "";
if (!isset($_POST['cat_title']) || empty($_POST['cat_title']) || $_POST['cat_title']=="") {
$cat_err = "field cannot be empty";
} else {
//check if a name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z]*$/", $_POST['cat_title'])) {
$cat_err = "Only letters and whitespace allowed";
}
}
//if no errors found
if ($cat_err=="") {
$cat_title = htmlentities($_POST['cat_title']);
$sql = "INSERT INTO categories(cat_title)VALUES('$cat_title')";
$insert = mysqli_query($link, $sql);
confirm_query($insert);
if (mysqli_affected_rows($link) == 1) {
$cat_err = "Category has been added";
redirect("categories.php");
} else {
$cat_err = "Adding category failed";
}
} else {
$cat_err = "Field cannot be empty";
}
return $cat_err;
}
}
?>
<?php $data=validate_post();echo $data;?><!-- call validate_post function-->
<!-- ADD CATEGORY FORM -->
<form action="" method="post">
<div class="form-group">
<label for="cat_tile">Categories</label>
<input type="text" class="form-control" name="cat_title" id="cat_tile"/>
</div>
<div class="form-group">
<input type="submit" class="btn btn-primary" value="+ Add Category" name="submit" >
</div>
</form>

Answer 3

Your function doesn't return any information. You need to tell it to return the errors, and then do something with them. You need to restructure the way messages are organized in your function, but the gist is this:
add return $error; to the end of your validate function.
Then in your page body:
<?php $errors = validate_post(); ?><!-- call validate_post function-->
<!-- ADD CATEGORY FORM -->
<form action="" method="post">
<?php
foreach($errors as $error)
{
echo $error;
}
?>
<div class="form-group">
So, change your validate function to save all messages into a single array, return the array, then process the items.
Variables declared inside a function only "exist" within the scope of that function. $post_info inside your function has no relationship to $post_info outside the function.

Answer 4

Try to pass in the $_POST array:
if (isset($_POST['submit'])){
validate_post($_POST)
}
function validate_post($post_array) {
// your code here
}
Matt first suggested this, but here is how you would do that.

Answer 5

Using your code this is the rundown to what you need to do for the function.
<?php
function validate_post($link, $data=[]) {
$error = array();
if (!isset($data['cat_title']) || empty($data['cat_title'])) {
$error[] = "field cannot be empty";
} else {
//check if a name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z]*$/", $data['cat_title'])) {
$cat_err = "Only letters and whitespace allowed";
}
}
//if no errors found
if (empty($error) && empty($cat_err)) {
$cat_title = htmlentities($data['cat_title']);
$sql = "INSERT INTO categories(cat_title)VALUES('$cat_title')";
$insert = mysqli_query($link, $sql);
confirm_query($insert); //This is another function you created???
if (mysqli_affected_rows($link) == 1) {
$post_info = "Category has been added";
redirect("categories.php");
} else {
$post_info = "Adding category failed";
}
} else {
$post_info = "Field cannot be empty";
}
}
if (isset($_POST['submit'])) {
include 'dbfile.php'; // Containing your db link variable if that is how you've done it
validate_post($link, $_POST); // Usually you need to pass your database link by reference also rather than by global.
}
?>
--html section--