Q:

how to retrieve text from text are with php on same page

I have a text-area, in which I need some text.
I simply need to get that text to be echoed out with PHP, while on the same page
This is my code so far:
<body>
    <br>
    <h1>Charles Dickens</h1>
    <form action="Charles Dickens.php" method="GET">
        <hr/>
        <textarea rows="20" cols="100" name="textTest">This a is the text Testing area.</textarea>
        <hr/>
    </form>

    <br>
    <br>

    <?php 
        $textTest = $_GET['textTest'];
        echo $textTest;
    ?>

</body>

for some reason it's give me an "undefined error", though the variable is defined:
textTest is undefined.

A:

I suggest you to change your file name as well:

it should be without space or with hyphens 

here you can like this, but you need to submit a form:
<?php
    if(isset($_GET["textTest"]){
    echo $_GET["textTest"];
    }
?>

If you don't want to submit form try it:
<script>
    $('#text-id').keypress(function() {
        var value = this.value;
        console.log(value);

    });
</script>

