Compartir url en redes sociales

La forma más sencilla:
https://www.addtoany.com/buttons/for/website

Generar el código y ponerlo en tu web (en el caso de Linkedin hace caso omiso a las metas de og, simplemente coge la primera imagen que encuentra)

API Linkedin (Mayo 2019)

En https://www.linkedin.com/developers/ registrar una nueva APP para obtener el client_id y client_secret (verificar tb la empresa a la que asocias dicha APP).

index.php:
require("config.php");
require("funciones.php");
getAuthorizationCode();

funciones.php:
if (! session_id()) {
    session_start();
}

function getAuthorizationCode() {
    $params = array(
        'response_type' => 'code',
        'client_id' => CLIENT_ID,
        'scope' => SCOPE,
        'state' => uniqid('', true), // unique long string
        'redirect_uri' => REDIRECT_URI,
    );

    // $url = 'https://www.linkedin.com/uas/oauth2/authorization?' . http_build_query($params);
$url = 'https://www.linkedin.com/oauth/v2/authorization?'.http_build_query($params);
    $_SESSION['state'] = $params['state'];
// echo $url;
    header("Location: $url");
    exit;
}

config.php:
define("CLIENT_ID", "77xxxx4hr97s30");
define("CLIENT_SECRET", "LRxxxxPZd2UgEV4Z");
define("REDIRECT_URI", "http://localhost/pruebas/linkedin/test_linkedin.php");
// define("SCOPE", 'r_basicprofile r_emailaddress');
define("SCOPE", "r_liteprofile r_emailaddress");

test_linkedin.php
require("config.php");
require("funciones.php");

$_SESSION['access_token'] = $_REQUEST["code"];
$url = "https://www.linkedin.com/oauth/v2/accessToken?grant_type=authorization_code&code=".$_GET["code"]."&redirect_uri=http://localhost/pruebas/linkedin/test_linkedin.php&client_id=".CLIENT_ID."&client_secret=".CLIENT_SECRET;

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL,$url."&format=json");
curl_setopt($ch, CURLOPT_POST, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$server_output2 = curl_exec ($ch);
curl_close ($ch);

if ($server_output2 === false) {
    exit("Error Number: " . curl_errno($ch) . "<br>Error String: " . curl_error($ch) . "<br>Info: " . print_r(curl_getinfo($ch), true));
} 
else {
    $obj = json_decode($server_output);
}

$_SESSION['access_token'] = $obj->access_token;
   
// sacar datos básicos
 $url = "https://api.linkedin.com/v2/me/?oauth2_access_token=".$_SESSION['access_token']; // ."&projection=(id,firstName,email-address)";
 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL,$url);
 curl_setopt($ch, CURLOPT_POST, 0);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 $server_output2 = curl_exec ($ch);
 curl_close ($ch);
 $user_data = json_decode($server_output2);
 echo "<br>Nombre: ".$user_data->firstName->localized->es_ES;
 echo "<br>Apellidos: ".$user_data->lastName->localized->es_ES;

 $url = "https://api.linkedin.com/v2/emailAddress?oauth2_access_token=".$_SESSION['access_token']."&q=members&projection=(elements*(handle~))"; //."&q=members&projection=(elements*(handle~))";
 $ch = curl_init();
 curl_setopt($ch, CURLOPT_URL,$url);
 curl_setopt($ch, CURLOPT_POST, 0);
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
 $server_output2 = curl_exec ($ch);
 curl_close ($ch);

 $user_data = json_decode($server_output2);
 // echo "<br>Email: ".$user_data->elements[0]->handle~->emailAddress;

  // print_r($user_data);

  foreach ($user_data->elements[0] as $clave=>$valor) {
  if (isset($valor->emailAddress)) {
  echo "<br>Email:".$valor->emailAddress;
  }
  }

Linkedin: Debug

https://www.linkedin.com/post-inspector/inspect/

Facebook, Twitter y Linkedin: Metas para compartir

<meta property="og:type" content="website"/>
  <meta property='og:url' content='https://www.youtube.com/watch?v=Kvj_qEPgPps' />
  <meta property="og:title" content="Atrápame si puedes (2002) de Steven Spielberg"/>
  <meta property="og:description" content="Atrápame si puedes (2002) de Steven Spielberg">
  <meta property="og:image" content="https://www.midominio.com/images/rrss/facebook.jpg">
  <meta name="twitter:card" content="summary"/>
  <meta name="twitter:url" content="https://www.youtube.com/watch?v=Kvj_qEPgPps"/>
  <meta name="twitter:title" content="Atrápame si puedes (2002) de Steven Spielberg"/>
  <meta name="twitter:description" content="Atrápame si puedes (2002) de Steven Spielberg"/>
  <meta name="twitter:image" content="https://i2.ytimg.com/vi/Kvj_qEPgPps/default.jpg"/>

Información de Twitter:
https://developer.twitter.com/en/docs/tweets/optimize-with-cards/overview/summary

Para Linkedin los metas son los mismos que Facebook pero es aconsejable también añadir:
<meta property="og:image:secure_url" content="https://www.midominio.com/images/rrss/linkedin.jpg">

Para chequearlo en FB:
https://developers.facebook.com/tools/debug/

Para chequearlo en Twitter:
https://cards-dev.twitter.com/validator

Para chequearlo en Linkedin:
https://www.linkedin.com/post-inspector/inspect/

Si en Twitter te diera el error de:
Fetching the page failed because it's denied by robots.txt

Para solucionarlo hay que poner en nuestro robots.txt:
User-agent: Twitterbot
 allow:

Más información en: https://www.flimper.com/blog/es/que-es-open-graph-y-como-se-hace

---

Ejemplo de compartir vídeo de YouTube:
<a href="https://www.facebook.com/sharer/sharer.php?u=https://www.youtube.com/watch?v=Y8UFpmqYTMY">xxx</a>

<a href="https://twitter.com/intent/tweet?url=https://www.youtube.com/watch?v=Y8UFpmqYTMY&text=prueba">xxx</a>

<a href="https://www.linkedin.com/sharing/share-offsite/?url=https://www.youtube.com/embed/Y8UFpmqYTMY">xxx</a>

<a href="https://api.whatsapp.com/send?text=https://www.youtube.com/watch?v=Y8UFpmqYTMY">xxx</a>

Ejemplo de compartir imagen:
<a href="https://www.facebook.com/sharer/sharer.php?u=https://www.midominio.com/imagenes/slide20191106105324.jpg">xxx</a>

<a href="https://twitter.com/intent/tweet?url=https://www.midominio.com/twitter.php?id=3">xxx</a>

En twitter.php debe tener los metas de twitter:
<?php
require("inc_config.php");
$sql = "SELECT * FROM mitabla where id = ".$id;
$db->query($sql);
$db->next_record();

$imagenShare = $base."imagenes/noticias/".$db->Record["imagen"];
$titleShare = $db->Record["titular"];
?>
<!DOCTYPE html>
<html>
<head>
  <meta name="twitter:card" content="summary" />
<meta name="twitter:site" content="@loquesea" />
<meta name="twitter:title" content="<?=$titleShare;?>" />
<meta name="twitter:description" content="<?=$titleShare;?>" />
<meta name="twitter:image" content="<?=$imagenShare;?>" />
  <meta property="og:image:secure_url" content="<?=$imagenShare;?>">
</head>
<body>
<img src="<?=$imagenShare;?>">
</body>
</html>

<a href="https://www.linkedin.com/sharing/share-offsite/?url=https://www.midominio.com/imagenes/slide20191105125558.jpg">xxx</a>

<a href="https://api.whatsapp.com/send?text=https://www.midominio.com/imagenes/slide20191105125558.jpg">xxx</a>


Linkedin: Obtener todos los datos de un perfil

Primero registrar una nueva APP en la API de Linkedin:
https://developer.linkedin.com

<?php
define('API_KEY','xxx');
define('API_SECRET','xxx');
define('REDIRECT_URI', $redirectURI); // puede ser localhost
define('SCOPE',  'r_basicprofile r_emailaddress rw_company_admin w_share');

session_name('linkedin');
session_start();

if (isset($_GET['error'])) {
    print $_GET['error'] . ': ' . $_GET['error_description'];
    exit;
} elseif (isset($_GET['code'])) {
    if ($_SESSION['state'] == $_GET['state']) {
        getAccessToken();
    } else {
        exit;
    }
} else {
    if ((empty($_SESSION['expires_at'])) || (time() > $_SESSION['expires_at'])) {
        $_SESSION = array();
    }
    if (empty($_SESSION['access_token'])) {
        getAuthorizationCode();
    }
}

$user = fetch('GET', '/v1/people/~:(id,firstName,lastName,skills,educations,pictureUrl,relationToViewer,positions,headline,location,industry,email-address,network)');
?>

El javascript:
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
<form id="form_reg_linkedin" name="form_reg_linkedin" action="<?=$rutaReg;?>" method="POST">
    <input type="hidden" name="nombre_completo" value="<?=$user->firstName;?> <?=$user->lastName;?>">
    <input type="hidden" name="email" value="<?=$user->emailAddress;?>">
    <?php
    require("../../config/cnnAux.php");
    $codPais = strtolower($user->location->country->code);
    $sql = "select * from paises where cod_pais = '".$codPais."'";
    $regPais = $app['db']->fetchAll($sql, array(
    ));
 
 
    $id_pais = 0;
    if (count($regPais) > 0)
        $id_pais = $regPais[0]["id"];
 
    $cp = "";
    if ($id_pais == 73) // España
        $cp = "28033";
 
 
    $azar = rand(1,999);
    $username = substr($user->firstName, 0,4)."_".substr($user->lastName, 0,4)."_".$azar;
    // Generar contraseña aleatoria
    $cadena = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
    $longitudCadena = strlen($cadena);
    $pass = "";
    $longitudPW = 10;
 
    for($i=1 ; $i<=$longitudPW ; $i++){
       $pos=rand(0,$longitudCadena-1);
       $pass .= substr($cadena,$pos,1);
    }
 
    $pos1 = strpos($user->location->name, " ");
    $ciudad = substr($user->location->name, 0, $pos1);
    ?>
    <input type="hidden" name="esRegLinkedin" value="1">
    <input type="hidden" name="id_pais" value="<?=$id_pais?>">
    <input type="hidden" name="otra_ciudad" value="<?=$ciudad?>">
    <input type="hidden" name="fecha_nacimiento" value="31/12/1977">
    <input type="hidden" name="nif" value="2222">
    <input type="hidden" name="cp" value="<?=$cp;?>">
    <input type="hidden" name="username" value="<?=$username;?>">
    <input type="hidden" name="pw1" value="<?=$pass;?>">
</form>

<script>
    $(function() {
       // alert("Enviar form");
       $("#form_reg_linkedin").submit();
    });
</script>

Funciones de PHP: <?php
exit;

function getAuthorizationCode() {
    $params = array(
        'response_type' => 'code',
        'client_id' => API_KEY,
        'scope' => SCOPE,
        'state' => uniqid('', true), // unique long string
        'redirect_uri' => REDIRECT_URI,
    );

    $url = 'https://www.linkedin.com/uas/oauth2/authorization?' . http_build_query($params);
    $_SESSION['state'] = $params['state'];
    header("Location: $url");
    exit;
}
   
function getAccessToken() {
    $params = array(
        'grant_type' => 'authorization_code',
        'client_id' => API_KEY,
        'client_secret' => API_SECRET,
        'code' => $_GET['code'],
        'redirect_uri' => REDIRECT_URI,
    );
     $url = 'https://www.linkedin.com/uas/oauth2/accessToken?' . http_build_query($params);

    $context = stream_context_create(
        array('http' =>
            array('method' => 'POST',
            )
        )
    );

    $response = file_get_contents($url, false, $context);

    $token = json_decode($response);

    $_SESSION['access_token'] = $token->access_token;
    $_SESSION['expires_in']   = $token->expires_in;
    $_SESSION['expires_at']   = time() + $_SESSION['expires_in'];
   
    return true;
}

function fetch($method, $resource, $body = '') {
    // print $_SESSION['access_token'];

    $opts = array(
        'http'=>array(
            'method' => $method,
            'header' => "Authorization: Bearer " . $_SESSION['access_token'] . "\r\n" . "x-li-format: json\r\n"
        )
    );

    $url = 'https://api.linkedin.com' . $resource;
 

    // if (count($params)) { $url .= '?' . http_build_query($params); }


    $context = stream_context_create($opts);

    $response = file_get_contents($url, false, $context);

    return json_decode($response);
}

?>