Parsear in PHP an XML that contains the character '

Good afternoon everyone.

I have made a php script to parse an XML file but this file in some of its fields contains the character ', which comes into conflict with the PHP code. At the moment I deleted this character from the XML file but I would like it to be stored in the DB.

I do not know if I should modify the XML file, putting something in front of the character so that when I read it the script does not enter into a conflict, or I must put something in the php script to free it. Can you help me?

I leave the php script:

$fichero = "./obras.xml";
if(!$xml = simplexml_load_file($fichero))
{
    echo "No se ha podido cargar el archivo <br>";
} 
else 
{
    echo "El archivo se ha cargado correctamente <br>";
}

include"./conectar.php";
$enlace= conectarse();

function Mayus($variable) {
$variable = strtr(strtoupper($variable),"àèìòùáéíóúçñäëïöü","ÀÈÌÒÙÁÉÍÓÚÇÑÄËÏÖÜ");
return $variable;
}

mysql_query("SET NAMES utf8");

foreach ($xml as $obra)
{
    $obra = (array) $obra;
    $ninv = $obra['ninventario'];

    $ninv = Mayus($ninv);
    $contrato = Mayus($obra['contrato']);
    $desc = Mayus($obra['titulo']); 

    $consulta ="INSERT INTO 'ficha' ('ninv', 'contrato', 'desc') VALUES ('".$ninv."','".$contrato."','".$desc."')"; 

    $resultado = mysql_query($consulta) or die(mysql_error()) ; 

    echo mysql_errno($enlace);
}

The error that occurs if the XML has the character 'is of this style:

  

You have an error in your SQL syntax near '12345678, 123.04, 0,)' at   line 2

Thank you very much.