PHP Form Validation with Multiple Input types

Question

I have a form with text inputs and a file upload. The code I have written below basically works (needs additional functionality which I will ask about in a separate question) but I'm wondering if there is a cleaner, more succinct way to write this. I am brand new to php and any help will be appreciated.

I want to display an error message per input if someone attempts to submit the form and a field is empty, or if the file type selected is not the correct type or size. In the code below I have a unique message displayed, but on second thought I could just say "required" if there is some way to make this code better by doing that.

I tried using jQuery validate plugin and couldn't get it to work with the file upload (it is beyond my understanding of jQuery/Ajax/PHP), so this is the solution I came up with.

        <?php require_once('../scripts/lcoa.php'); ?>
        <?php 
        if (isset($_GET['jobid'])) {
        $jobid = $_GET['jobid'];
        }
        if (isset($_GET['jobtitle'])) {
        $jobtitle = $_GET['jobtitle'];
        }
         //This is the directory where resumes will be saved 
        $target = "../careers/resumes/"; 
        $target = $target . basename( $_FILES['resume']['name']); 
        $resume=($_FILES['resume']['name']);
        $type = ($_FILES['resume']['type']);
        $extension = strtolower(substr($resume, strpos($resume, '.') + 1)); 
        $size = ($_FILES['resume']['size']);
        $max_size = 3145728;
        $name  = ($_POST['name']);
        $email  = ($_POST['email']);
        $phone  = ($_POST['phone']);
        $jobid = ($_POST['jobid']);
        $jobtitle = ($_POST['jobtitle']);
        $cover = ($_POST['coverletter']);

        if(isset($name)){
            if (empty ($name)){
                ?>
                <script type="text/javascript">
                    $(document).ready(function() {
                       $('#applicant-name').before('<p class="error">Please provide your full name. </p>');          
                    });
                </script> 
                <?php
            }
        }
        if(isset($email)){
            if (empty ($email)){
                ?>
                <script type="text/javascript">
                    $(document).ready(function() {
                       $('#applicant-email').before('<p class="error">Please provide your email address. </p>');          
                    });
                </script> 
                <?php
            }
        }
        if(isset($phone)){
            if (empty ($phone)){
                ?>
                <script type="text/javascript">
                    $(document).ready(function() {
                       $('#applicant-phone').before('<p class="error">Please provide a phone number. </p>');          
                    });
                </script> 
                <?php
            }
        }

        //Writes the resume to the server 
        if (isset ($resume)) {
            if (!empty ($resume)){
                if(($extension=='doc'||$extension=='docx'||$extension=='txt'||$extension=='pdf')&&($type=='application/pdf'||'application/msword'||'application/vnd.openxmlformats-officedocument.wordprocessingml.document'||'text/plain')&&$size<=$max_size) {
                if(move_uploaded_file($_FILES['resume']['tmp_name'], $target)) { 
                     //Writes the information to the database 
                $insertSQL = "INSERT INTO applicants (id, name, email, phone, jobid, jobtitle, coverletter, resume) VALUES ('','".$_POST['name']."','".$_POST['email']."','".$_POST['phone']."','".$_POST['jobid']."','".$_POST['jobtitle']."','".$_POST['coverletter']."','".$resume."')";
                mysql_select_db($database_lcoa, $lcoa);
                $Result1 = mysql_query($insertSQL, $lcoa) or die(mysql_error());

                     //Tells you if its all ok 
                     echo "<div id='confirm-app'><p>Thank you for submitting your application.  Resumes submitted will be reviewed to determine qualifications that match our hiring needs.<br /><br />  If you are selected you will be contacted by a member of our recruiting team.</p><br /><br /><a href='../careers/job-postings.php'>Return to current opportunities</a></div>"; 
                     }
                }       
                     else { 
                     //Gives and error if its not 
                     echo "<p style='color: #6D6E71; font-family: Arial,Helvetica,sans-serif; font-size: 13px;'>We accept resumes in <strong>.doc</strong>, <strong>.docx</strong>, <strong>.pdf</strong>, or <strong>.txt</strong> formats, 3MB or less. Please <a href='javascript:history.back(-1);'>go back</a> to upload a file that meets these requirements.<br /><br />If you continue to experience errors, please report them.</p>"; 
                     die();
                     } 
                }
                else {
                     ?>
                         <script type="text/javascript">
                            $(document).ready(function() {
                               $('#upload-resume').before('<p class="error">Please select a file to upload. </p>');          
                            });
                        </script> 
                     <?php
                }
        }       
         ?> 

Answer 1

Just giving you an idea for few fields for other fields try it by your self

    //php
    $name=$_POST['name'];
    $email=$_POST['email'];
    $error=array();
    if(isset($name)){
        if (empty ($name)){
     $error['name']="<p class='error'>Please provide your full name. </p>";
        }
    }
    if(isset($email)){
        if (empty ($email)){
     $error['email']="<p class='error'>Please provide correct email. </p>";
        }
    }

    //HTML 

<form action="" name"myform">

<?php if(!empty($error['name'])){ echo $error['name']; } ?>

<input type="text" name="name" value="<?php if(isset($name)){ echo $name; } ?>"/>

<?php if(!empty($error['email'])){ echo $error['email']; } ?>

<input type="text" name="name" value="<?php if(isset($name)){ echo $name; } ?>"/>

</form>

Its just an idea to show you same logic while validating for file upload or have to use regex test for phone , email etc

Hope it makes sense