Custom Fields

Hey guys I have this script that works well

<?php
//amazon api

define('AWS_ACCESS_KEY_ID', 'AKrrIArJusgOV4ZWjghjhjUB2QSUL6KAjghj');
define('AWS_SECRET_ACCESS_KEY', 'JzTISpVdghdfhdfhfdhdfhdfh8JxmRaVXmaJI8C4Izc9tEywCwk');
define('AMAZON_ASSOC_TAG', 'chehdfhdhdfhdfh20');

function amazon_get_signed_url($searchTerm) {
$base_url = "https://ecs.amazonaws.com/onca/xml";
$params = array(
'AWSAccessKeyId' => AWS_ACCESS_KEY_ID,
'AssociateTag' => AMAZON_ASSOC_TAG,
'Version' => "2010-11-01",
'Operation' => "ItemSearch",
'Service' => "AWSECommerceService",
'ResponseGroup' => "ItemAttributes,Images",
'Availability' => "Available",
'Condition' => "All",
'Operation' => "ItemSearch",
'SearchIndex' => 'All', //Change search index if required, you can also accept it as a parameter for the current method like $searchTerm
'Keywords' => $searchTerm);

//'ItemPage'=>"1",
//'ResponseGroup'=>"Images,ItemAttributes,EditorialReview",

if(empty($params['AssociateTag'])) {
unset($params['AssociateTag']);
}

// Add the Timestamp
$params['Timestamp'] = gmdate("Y-m-d\TH:i:s.\\\\\Z", time());

// Sort the URL parameters
$url_parts = array();
foreach(array_keys($params) as $key)
$url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key]));
sort($url_parts);

// Construct the string to sign
$url_string = implode("&", $url_parts);
$string_to_sign = "GET\necs.amazonaws.com\n/onca/xml\n" . $url_string;

// Sign the request
$signature = hash_hmac("sha256", $string_to_sign, AWS_SECRET_ACCESS_KEY, TRUE);

// Base64 encode the signature and make it URL safe
$signature = urlencode(base64_encode($signature));

$url = $base_url . '?' . $url_string . "&Signature=" . $signature;

return ($url);
}

?>
<?php

 $lcolor = 000 ;
 $web_rank = 'myid';

$getthis = 'My keyword';

$show = amazon_get_signed_url($getthis);

$ch = curl_init($show);
curl_setopt($ch, CURLOPT_HEADER, false);
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
$c = curl_exec($ch);

$xml = simplexml_load_string($c);
$json = json_encode($xml);
$array = json_decode($json,TRUE);

$checkamazon = $array['Items']['Item'][0]['DetailPageURL'];

if($checkamazon != ""){
}

for($i=0;$i<1;$i++){

$aprice = $array['Items']['Item'][$i]['ItemAttributes']['ListPrice']['FormattedPrice'];
$aDescription = $array['Items']['Item'][$i]['ItemAttributes']['Title'];
$aUrl = $array['Items']['Item'][$i]['DetailPageURL'];
$aImage = $array['Items']['Item'][$i]['SmallImage']['URL'];

if($aUrl != ""){
echo "<a href = \"$aUrl\" target='_blank' STYLE=\"TEXT-DECORATION: NONE;\">";
echo "<img src='$aImage' ><p>$aDescription</p></a><br>";

}
}

?>

Everythin works well if in the $getthis variable I write an keyword.
It echo’s the amazon product.

Now I’ve set up an custom field <?php meta('Key1'); ?>

I want the variable $getthis to be equal to this custom field

I tried
$gethis = meta('Key1'); dont work
$gethis = "meta('Key1')"; only echo the actual keyword that is set in the custom field

Please help