Retrieve Product's info using API:

mage-product-api.php

<?php
// Check product's status. 
function getProductInfo($product_id){
 
            $this->APIUrl= "http://yourdomain.com/index.php/api/soap/?wsdl";
        $this->APIUser="APIUser";
        $this->APIKey= "APIKey";
                $proxy = new SoapClient($this->APIUrl);
        $sessionId = $proxy->login($this->APIUser, $this->APIKey);
           $exists = true;
    try {
        $info = $proxy->call($sessionId, 'product.info', $product_id);
    } catch (SoapFault  $e){
        $exists= false;
    }
    return $exists;
}
?>
<?php
// Update Product's Info
function updateProductInfo(){
 
            $this->APIUrl= "http://yourdomain.com/index.php/api/soap/?wsdl";
        $this->APIUser="APIUser";
        $this->APIKey= "APIKey";
                $proxy = new SoapClient($this->APIUrl);
        $sessionId = $proxy->login($this->APIUser, $this->APIKey);
    $filters = array(
    'sku' => array('like'=>'somesku%')
    );
    try {
        $products = $proxy->call($sessionId, 'product.list', array($filters));
                $numProducts = sizeof($products);
        for($i=0;  $icall($sessionId, 'product.update',array($products[$i]['sku'], array('name'=>$new_product_name, 'meta_keyword'=>$new_meta_keyword,'meta_description'=>$new_meta_description,'meta_title'=>$new_meta_title)));
        }
    } catch (SoapFault  $e){
        echo $e->getMessage();
    }
    return true;
}