PHP Form to Insert data in Database -

i've created form inserts data database. i've been given 2 functions data , display it, these located in file called querydb.php:

function addcustomer($fname, $lname, $address, $phone) {     $db = new mydb();     if(!$db){         echo '<script type="text/javascript">alert("'.$db->lasterrormsg().'");</script>';     } else {         //echo "opened database successfully\n";     }      $sql ='insert customers (firstname, lastname, address, phone) values ("'.$fname.'", "'.$lname.'", "'.$address.'", "'.$phone.'");';     $db->query($sql); } 

get function:

function getcustomers($searchterm = null) {           $db = new mydb();      if(!$db){         echo '<script type="text/javascript">alert("'.$db->lasterrormsg().'");</script>';     } else {         //echo "opened database successfully\n";     }      if(!$searchterm) {         $sql ='select * customers;';     } else {         $sql ='select * customers firstname "'.$searchterm.'" or lastname "'.$searchterm.'" or address "'.$searchterm.'" or phone  "'.$searchterm.'"';     }     $ret = $db->query($sql);     $array = [];      if(!$ret){        echo $db->lasterrormsg();        return [];     } else {         while($row = $ret->fetcharray(sqlite3_assoc) ){             $array[] = $row;         }         $db->close();         return $array;     } } 

in reviewsubmit.php have top:

<?php     require_once "querydb.php";     $firstname = $_post["firstname"];     $lastname = $_post["lastname"];     $address = $_post["address"];     $phone = $_post["phone"];     addcustomer($firstname, $lastname, $address, $phone); ?> 

and form:

<form action="reviewsubmit.php" method="post">     firstname     <input type="text" id="firstname" name="firstname">  />     lastname     <input type="text" id="lastname" name="lastname"">  />     address     <input type="text" id="address" name="address">  />     phone     <input type="text" id="phone" name="phone">  />     <input type="submit" name="submit" value="submit" /> </form> 

the problem when submit information database using form, submits empty values when click submit first time. when hit submit again submits actual values: image

your html mark-up not best , cause anomalies. simultaneously, ideal add required attribute fields ensure necessary fields filled before submitting so:

<!-- guard against accidentally inserting empty values --> <!-- why not make input fields mandatory --> <form action="reviewsubmit.php" method="post">     <label for="firstname">firstname</label>     <input type="text" id="firstname" name="firstname" required  />      <label for="lastname">lastname</label>     <input type="text" id="lastname" name="lastname" required />      <label for="address">address</label>     <input type="text" id="address" name="address" required />      <label for="phone">telephone</label>     <input type="text" id="phone" name="phone" required/>      <input type="submit" name="submit" value="submit" /> </form> 

on php side, may go mile of checking submitted values not empty or null before submitting database. way both sure of going on @ front , back-ends. way of doing that:

<?php     // file: index.php     require_once "querydb.php";     $firstname  = isset($_post["firstname"])? htmlspecialchars(trim($_post["firstname"]))   : null;     $lastname   = isset($_post["lastname"]) ? htmlspecialchars(trim($_post["lastname"]))    : null;     $address    = isset($_post["address"])  ? htmlspecialchars(trim($_post["address"]))     : null;     $phone      = isset($_post["phone"])    ? htmlspecialchars(trim($_post["phone"]))       : null;      // check don't have null or empty field values before inserting database     if(!is_null($firstname) && !is_null($lastname) && !is_null($address) && !is_null($phone) ){         addcustomer($firstname, $lastname, $address, $phone);     }  ?>