ReCaptcha et PHP

$recaptcha = !empty($_POST['g-recaptcha-response']) ? $_POST['g-recaptcha-response'] : NULL;

$recaptcha = !empty($_POST['grecaptcharesponse']) ? $_POST['grecaptcharesponse'] : NULL;

$(function() {

    $("input,textarea").jqBootstrapValidation({
        preventSubmit: true,
        submitError: function($form, event, errors) {
            // additional error messages or events
        },
        submitSuccess: function($form, event) {
            // Prevent spam click and default submit behaviour
            $("#btnSubmit").attr("disabled", true);
            event.preventDefault();
            
            // get values from FORM
            var sex = $("select#sex").val();
            var name = $("input#name").val();
            var email = $("input#email").val();
            var message = $("textarea#message").val();
            var phone = $("input#phone").val();
            $.ajax({
                url: "././mail/mail.php",
                type: "POST",
                data: {
                    name: name,
                    email: email,
                    message: message,
                    phone: phone,
                    sex: sex,
                    grecaptcharesponse:$("input#g-recaptcha-response").val();
                },
                cache: false,
                success: function(reponse) {
                    console.log(reponse);
                  
                    // Enable button & show success message
                    $("#btnSubmit").attr("disabled", false);
                    $('#success').html("<div class='alert alert-success'>");
                    $('#success > .alert-success').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>×")
                        .append("</button>");
                    $('#success > .alert-success')
                        .append("<strong>Votre message a bien été envoyé. Je reviendrai vers vous dans les plus brefs délais.</strong>");
                    $('#success > .alert-success')
                        .append('</div>');

                    //clear all fields
                    $('#contactForm').trigger("reset");
                },
                error: function(errormsg) {
                  console.log(errormsg);
                    // Fail message
                    $('#success').html("<div class='alert alert-danger'>");
                    $('#success > .alert-danger').html("<button type='button' class='close' data-dismiss='alert' aria-hidden='true'>×")
                        .append("</button>");
                    $('#success > .alert-danger').append("<strong>Désolé " + name + ", on dirait que le serveur mail ne répond pas... :( Veuillez réessayer plus tard.");
                    $('#success > .alert-danger').append('</div>');
                    //clear all fields
                    $('#contactForm').trigger("reset");
                },
            })
        },
        filter: function() {
            return $(this).is(":visible");
        },
    });

    $("a[data-toggle=\"tab\"]").click(function(e) {
        e.preventDefault();
        $(this).tab("show");
    });

});

$recaptcha = !empty($_POST['g-recaptcha-response']) ? $_POST['g-recaptcha-response'] : NULL;

$recaptcha = !empty($_POST['grecaptcharesponse']) ? $_POST['grecaptcharesponse'] : NULL;

<?php
//------------------------------------------------------------------
//activation affichage des erreurs
//------------------------------------------------------------------
error_reporting(E_ALL);
ini_set('display-errors','on');

//------------------------------------------------------------------
//le temps des tests:
//affichage des variables POST
//------------------------------------------------------------------
  echo "<pre> POST :<br>";
  print_r($_POST);
  echo "</pre>";

//------------------------------------------------------------------
//récupération PROPRE des variables AVANT de les utiliser
//------------------------------------------------------------------
$name = !empty($_POST['name']) ? $_POST['name'] : NULL;
$email_address = !empty($_POST['email']) && filter_var($_POST['email'],FILTER_VALIDATE_EMAIL) ? $_POST['email'] : NULL;
$message = !empty($_POST['message']) ? $_POST['message'] : NULL;
$phone = !empty($_POST['phone']) ? $_POST['phone'] : NULL;
$sex = !empty($_POST['sex']) ? $_POST['sex'] : NULL;

$recaptcha = !empty($_POST['grecaptcharesponse']) ? $_POST['grecaptcharesponse'] : (!empty($_POST['g-recaptcha-response']) ? $_POST['g-recaptcha-response'] : NULL);
 if(!$name  ||!$email_address || !$message  || !$phone  ||  !$sex){
    echo "Pas de données envoyées!";
    $result =  false;
  }
    
 
 //------------------------------------------------------------------
 // Traitement du formulaire
 //------------------------------------------------------------------
 $result = "";
 if($recaptcha){
    //your site secret key
    $secret = 'ma clé secrète';
    //get verify response data
    $verifyResponse = file_get_contents('https://www.google.com/recaptcha/api/siteverify?secret='.$secret.'&response='.$recaptcha);
    $responseData = json_decode($verifyResponse);
    
    //pour tester :
     print_r($responseData);
    
    if($responseData->success){  
   
     //Envoi du mail
     $to = 'Mon adresse mail';
     $email_subject = "Site web";
     $email_body = "Site web.\n\n$sex $name\n\nEmail: $email_address\n\nTéléphone: $phone\n\nMessage:\n$message";
     $headers = "From: robot@adresse de mon site web\n";
     if(mail($to,$email_subject,$email_body,$headers)){
       echo "email envoyé";
       $result =  true;  
     }else{
       echo "Erreur lors de l'envoie de l'email ";
       $result =  false;
     }
       
   }else{
     
      echo "Merci de cocher la case.";
     $result =  false;
   } 
 }else{
   echo " recaptcha est vide !";
 } 
 
 return $result;
?>