function empty_check($var){ // Start Function
	if(is_array($var)){ // Determine if $var is an array or not
		foreach($var as $key => $value){ // If it is an array go through the array and assign to $key and $value
			$value = trim($value); // Remove any whitespace from the start and end of the value
			if(empty($value)){ // Check if its empty or not
				$empty[] = $key; // If its empty put the name of the field thats empty in $empty array.
			}
		}
	}else{ // If it isnt in an array
		$var = trim($var); // Remove any whitespace from the start and end of the value
		if(empty($var)){ // Check if its empty or not
			$empty[] = $var; // If its empty put the value into the $empty array.
		}
	}
	return $empty; // Return $empty.
}

<?php

if($_POST['submit']){
	$empty = empty_check($_POST);
	if($empty){
		echo "You have left the following fields empty<br />";
		foreach($empty as $value){
			echo $value . ", ";
		}
	}else{
		echo "All fields are filled in.";
	}
}

?>
<form method="post" action="">
	<input type="text" name="first_name" />
	<input type="text" name="last_name" />
	<input type="submit" value="Submit Button" name="submit" />
</form>

explode  ( string $delimiter  , string $string  [, int $limit  ] )

<?php

$string = "Peter;Mark;Rupert;Jack;Harold;Daniel"; // String containing names seperated by ;
$explode = explode(";",$string); // Delimiter is the ; which is seperating the names and then the $string.

print_r($explode); // Prints out the array $explode.

echo $explode[1]." is friends with ". $explode[5]; // Mark is friends with Daniel

?>

 » Read more: [PHP Tutorial] How to use Explode

function store_encrypt($array)
{ // Start function with function name store_encrypt.
    if (!is_array($array))
    { // Check if $array is an array or not if it isnt return false.
        return false; // return false.
    }
    else
    {
        foreach ($array as $key => $value)
        { // Cycle through the array.
            $key = base64_encode($key); // Encode the key with base 64.
            $value = base64_encode($value); // Encode the value with base 64.

            $array[$key] = $value; // Put the key and value back into the array
        }
        return serialize($array); // Use the PHP serialize function to save the array, type and values and return the function.
    }
}

 » Read more: [PHP Tutorial]  Store An Array