PHP - Controls Not Working After Form Filled

How is it possible, in PHP, to display an error message next to a form input text field if a user is attempting to submit a form with empty fields? Moreover, how is it possible to remove the same error message when the user fills in the input field with the required data and/or refreshes the page?

I have 2 files that I am working with: application.php and process.php.

application.php mainly has the HTML of the form.
process.php has the PHP for processing and validating the form.

I am very new to learning PHP (I started learning it last week) and I have been searching for hours for a clear answer. I have already tried different methods for generating the error message including: using empty(), !isset, $_POST["name"] = "", etc, and have tried using session_start();, $row, echo, print, and other variables to try and display error message on the page, and I have tried using unset();, and = null, to try and remove the error message once the input field has been filled but all to no avail. Either the method I try only half works, or nothing works, and I cannot pinpoint which is the part that is not working.

I only have 2 files to work with, and as an example of what I want to do is:

1. If the first name field is empty when the user clicks submit, an error message should appear next to the input.
2. If the user fills in the input and clicks submit, the form should be processed and added to the database.
3. When the user returns to the application to page to fill in another application form, the error message should not appear.

Is this possible with PHP?

Hello friends;

Is there a controls for php like asp (Grid-dropbox - listbox) and so on 

and what is best editor for php

Thank you so much

 <?php  
             
            function displayRequired($fieldName) { 
                echo " \".$fieldName\"is required.<br />n"; 
            } 
             
            function validateInput($data, $fieldName){ 
                global $errorCount; 
                if (empty($data)){ 
                    displayRequired($fieldName); 
                    ++$errorCount; 
                    $retval = ""; 
                } else { 
                    $retval = trim($data); 
                    $retval = stripslashes($retval); 
                } 
                return ($retval); 
            } 
             
            $Deposition = validateInput(safe($_POST['deposition']), "Deposition");
			$Time = validateInput(safe($_POST['time']), "Time");
			$Delivery = validateInput(safe($_POST['delivery']), "Delivery");
			$Witness = validateInput(safe($_POST['witness']), "Witness");
			$Location = validateInput(safe($_POST['location']), "Location");
			$Attorney = validateInput(safe($_POST['attorney']), "Attorney");
			$Name = validateInput(safe($_POST['name']), "First Name"); 
			$Firm = validateInput(safe($_POST['firm']), "Firm Name"); 
			$Phone = validateInput(safe($_POST['phone']), "Phone");
            $Email = validateInput(safe($_POST['email']), "Email"); 
           
			
            
             
             
            if ($errorCount>0){ 
                echo "Please re-enter the information below.<br />\n"; 
                redisplayForm($Deposition, $Time , $Ampm, $Timeday, $Delivery, $Video, $Co1, $Co2, $Witness, $Location, $Additional, $Attorney, $Name, $Firm, $Address, $Phone, $Fax, $Email); 
            } 
            else 
             
            {     
                $To = "service@rodriguezstudios.com"; 
                $Subject = "The test"; 
                $From = "Schedule a Deposition - Professional Court Reporters"; 
             
				 
				 $Message .= "Deposition Date:  " . $Deposition . "\n";
				 $Message .= "Time: " . $Time . $Ampm. $Timeday . "\n\n";
				 $Message .= "Transcript Delivery: " . $Delivery . "\n\n\n";
				 $Message .= "Video:  " . $Video . "\n\n\n\n";
				 $Message .= "Case Option: " . $Co1. "vs: " . $Co2 . "\n\n\n\n\n";
				 $Message .= "Witness: " . $Witness . "\n\n\n\n\n\n";
				 $Message .= "Location:  " . $Location . "\n\n\n\n\n\n\n";
				 $Message .= "Additional Requests: " . $Additional. "\n\n\n\n\n\n\n\n";
				 $Message .= "Attorney Name: " . $Attorney . "\n\n\n\n\n\n\n\n\n";
				 $Message .= "Your Name:  " . $Name . "\n\n\n\n\n\n\n\n\n\n";
				 $Message .= "Firm Name: " . $Firm. "\n\n\n\n\n\n\n\n\n\n\n";
				 $Message .= "Firm Physical Address: " . $Address . "\n\n\n\n\n\n\n\n\n\n\n\n";
				 $Message .= "Phone No:  " . $Phone . "\n\n\n\n\n\n\n\n\n\n\n\n\n";
				 $Message .= "Fax No: " . $Fax. "\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
				 $Message .= "Email: " . $Email . "\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n";
				 
                $Headers = "From: ". $From . "<" . $To. ">\r\n";   
                $Headers .= "Reply-To: " . $Email . "\r\n";  
                $Headers .= "Return-path: ". $Email; 
                $result = mail($To, $Subject, $Message, $Headers); 
                if ($result) 
                    $resultMsg = "You message was sucessfully sent."; 
                    else 
                    $resultMsg = "There was a problem sending your message."; 
				
				/*insert anti spam fragement here */
				
             ?>
       <p style="line-height:200%; text-align:center; font-family:Verdana, Geneva, sans-serif; color:#000000">Your deposition has been scheduled<?php 
                        if(!empty($fieldName)) { 
                            echo " , {$fieldName}. {$resultMsg}"; 
                        } 
                         
                    echo "</p>"; 
                } 
                ?> 
     
            
         <?php 
               function redisplayForm($Deposition, $Time , $Ampm, $Timeday, $Delivery, $Video, $Co1, $Co2, $Witness, $Location, $Additional, $Attorney, $Name, $Firm, $Address, $Phone, $Fax, $Email){ 
             
            ?> 
            
            
            
             <form action="" method="POST">
     <fieldset class="first">
            <fieldset class="first">
    <p>
      <label class="labelone"for="deposition">*Deposition Date:</label>
      <input type="text" id="datepicker" name="deposition" value="<?php echo $Deposition; ?>" />
    </p>
    <p>
      <label for="*Time:" name="time">*Time: </label>
      <input type="text" name="time" value="<?php echo $Time; ?>">
      <select name="ampm" id="Ampm">
        <option value="am">A.M.</option>
        <option value="pm">P.M.</option>
      </select>
      <select name="timeday" id="Timeday">
        <option value="all">All Day</option>
        <option value="half">Half Day</option>
        <option value="hours">1-2 hrs</option>
      </select>
    </p>
    <p>
      <label for="*Transcript Delivery:" name="transcript"/>
      *Transcript Delivery:</label>
      <select>
        <option value="regular">Regular Delivery (10 day)</option>
        <option value="same">Same Day</option>
        <option value="1day">1 Day</option>
        <option value="2day">2 Day</option>
        <option value="3day">3 Day</option>
        <option value="4day">4 Day</option>
        <option value="5day">5 Day</option>
      </select>
    </p>
    <p>
      <label for="*Video" name="video">*Video:</label>
        <select name="video" id="video">
          <option value="yes">Yes</option>
          <option value="no">No</option>
        </select>
      </label>
    </p>
    <p>
      <label for ="caseoption">Case Option:</label>
      <input type="text" name="co1" value="<?php echo $Co1; ?>"/>
      vs.
      <input type="text" name="co2" value="<?php echo $Co2; ?>" />
    </p>
    <p>
      <label for ="witness">*Witness:</label>
      <input type="text" name="witness" value="<?php echo $Witness; ?>" />
    </p>
  </fieldset>
  <fieldset>
    <legend>LOCATION OF DEPOSITION, TELEPHONE NUMBER, AND NAME OF CONTACT PERSON:</legend>
    <p>
      <label for="location">*Location:</label>
      <textarea name="location" id="Location" value="<?php echo $Location; ?>"></textarea>
    </p>
    <p>
      <label for="additional">Addtional Requests (i.e. Realtime):</label>
      <input type="text" name="additional" value="<?php echo $Additional; ?>" />
    </p>
    <p>
      <label for ="attorney">*Attorney Name:</label>
      <input type="text" name="attorney" value="<?php echo $Attorney; ?>" />
    <p>
      <label for ="name">*Your Name:</label>
      <input type="text" name="name" value="<?php echo $Name; ?>" />
    </p>
    <label for ="firm">*Firm Name:</label>
    <input type="text" name="firm" value="<?php echo $Firm; ?>" />
    </p>
    <p>
      <label for ="firmaddress">Firm's Physical Address:</label>
      <input type="text" name="address" value="<?php echo $Address; ?>" />
    </p>
    <p>
      <label for ="phone">*Phone No:</label>
      <input type="text" name="phone" value="<?php echo $Phone; ?>"/>
    </p>
    <p>
      <label for ="fax">Fax No:</label>
      <input type="text" name="fax" value="<?php echo $Fax; ?>"/>
    </p>
    <p>
      <label for ="email">*Email:</label>
      <input type="text" name="email" value="<?php echo $Email; ?>" />
    </p>
  </fieldset>
  <fieldset>
    <input class="btn" name="submit" type="submit" value="Send Email"/>
    <input class="btn" name="reset" type="reset" value="Clear Form" />
  </fieldset>   
    </form>
     
		<?php 
            } 
            ?>


<?php 
function safe($string) 
	{ 
		$pattern = "/\r|\n|\%0a|\%0d|Content\-Type:|bcc:|to:|cc:/i"; 
		return preg_replace($pattern, '', $string); 
	}
?>