How to use double and single quotes in a string in PHP to go to MYSQL?

I recommend that for a simpler understanding of the string you use a statement with parameters:

//Escapamos el caracter " como \"
$variable= "Tuberia de acero al carbono Ø4\" sch 40 ;";

$idDetalle = 1;

//No conozco los detalles de tu conexion, asumire que tenes una variable $conn

//Los signos de interrogacion es donde iran los parametros
$sql = "INSERT INTO detalle (idDetalle,variable) VALUES (?,?);";

//Preparamos la sentencia
$stmt = $conn->prepare($sql);

//Asociamos los parametros a las variables, 
//La cadena "is" significa que el primer parametro sera un entero i
//y el segundo parametro sera una cadena s
$stmt->bind_param("is",$idDetalle,$variable);

//Ejecutamos la sentencia
$stmt->execute();

//Cerramos la sentencia
$stmt->close();

Try to insert the insertion code so

$cadena_insertar .= '( " ' . $idDetalle . '  ",".chr(34).$variable.chr(34).")';

the chr (34) is an ascii character, the 34 that is the one of my answer is comillas ("), I put this answer because once I had the same problem and this I solve it

Another way can be with Interpolated Chains

When the string starts with double quotes, the variables can be passed in the same string and replaced by their values at run time

$string0 = 'PHP';
$string1 = 'Cadenas';
echo "$string0 acepta $string1 interpoladas";
//output: PHP acepta Cadenas interpoladas

So you can do something like

$sql = "INSERT INTO detalle (idDetalle,variable) VALUES ($idDetalle ,$variable);";