JSEncrypt can sign and verify but PHP openssl_verify fails

Question

JSEncrypt can sign and verify but PHP openssl_verify fails

Using JSEncrypt to sign/verify a message works fine. However when I send the data to a PHP server for verification using openssl_verify it returns:

error:0906D06C:PEM routines:PEM_read_bio:no start line

Any idea why?

//////////////browser side
var signatory = new JSEncrypt();
var privateKey = document.getElementById("privkey").value;
signatory.setPrivateKey(privateKey);
var message = document.getElementById("pseudo").value;
var rsa_sha256_signature = signatory.sign(message, CryptoJS.SHA256);
document.getElementById("email").value = rsa_sha256_signature;
console.log("signature: " + rsa_sha256_signature);

    /* verify */
    var verifier = new JSEncrypt();
    var publicKey = document.getElementById("pubkey").value;
    
    verifier.setPublicKey(publicKey);
    if (verifier.verify(message, rsa_sha256_signature, CryptoJS.SHA256)) {
     console.log("valid signature !");
    }else{
        console.log("invalid signature!")
    }  
    
/////////////data is sent to server:
req.open("POST", "sign.php", true); 
req.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); 

var donnees = "message=" + document.getElementById('pseudo').value +
                        "&signature=" + document.getElementById('email').value +
                        "&key_pub=" + document.getElementById("pubkey").value;

req.send(donnees );     
    
/////////////server side        
$message = $_POST ['message'];

$entityBody = file_get_contents('php://input');
$detach = explode("&",$entityBody);

$cherche_signature = 'signature=';
$cherche_key_pub = 'key_pub=';


$foundEncryptedText="no";
foreach($detach as $value){
  if (strpos($value, $cherche_signature) !== false) {
      $found_signature = substr($value, strlen($cherche_signature));
  }
  if (strpos($value, $cherche_key_pub) !== false) {
      $foundkey_pub = substr($value, strlen($cherche_key_pub));
  }

}

$result = openssl_verify( $message , $found_signature , $foundkey_pub , OPENSSL_ALGO_SHA256 );
echo "valid= " . $result;
echo "erreur : <br>".openssl_error_string();