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josanangel
Asked: 2020-06-20 01:13:16 +0800 CST 2020-06-20 01:13:16 +0800 CST

Check if a field is empty before inserting it with PHP

  • 772

I want to insert data in my DB, but first I want to check if the field is empty, if it is, I want to replace it; change : ''to null, but it doesn't, it keeps leaving it as an empty string , that is: ''.

This comes from the form:

$fecha_nacimiento= $_POST['fecha_nacimiento'];

So I do the following:

        if (strlen(trim($fecha_nacimiento)) == 0) {
            $fecha_nacimiento = null;   
        }

Doing echoa strlen(trim($fecha_nacimiento))sample 0. But it does not go through the ifone I have put.

I want to do this because I have a variable $sqlwith the insert, and if it goes through the if I put it to null and if not what I receive.

I receive the dates from inputa type : date.

$sql = "INSERT INTO familiares(fecha_nacimiento) VALUES('".$fecha_nacimiento ."');";

The thing is that it gives an error if I insert a string without DATE format in the DB. For what I wanted to control with an if that tells me, if it is ( .length == 0) that I put it in null. But it doesn't.

CLARIFICATION : The error is not that it puts 'NULL'instead of NULLand detects it as a string, but rather that var_dump()it (whether .length == 0or not) always returns ''.

php

3 Answers

  1. Best Answer

    The ifone you have suggested works fine. With an empty string the variable $fecha_nacimientowill be set to value NULL.

    The problem is elsewhere. More specifically in insert:

    $sql = "INSERT INTO familiares(fecha_nacimiento) VALUES('".$fecha_nacimiento ."');";

    When you try to print the value of a variable whose value is NULLyou won't get the word NULL, since variables of this type don't have conversion to string, as do variables of type boolean, so what you insert're really doing:

    $sql = "INSERT INTO familiares(fecha_nacimiento) VALUES("");";

    Without seeing the rest of your code, a possible solution would be the use of prepared statements , which would allow you to pass queriea variable with a value to NULLit and also make your application more secure by controlling SQL injection.

    • 5

  2. I see no way to fail the if; unless it's a special character, which you could check with mb_strlen. Maybe the problem is in the after handling.

    The rules are: trim(null) = ''and isset('') = true.

    Therefore: isset(trim(null)) = true.

    $sql = "INSERT INTO familiares(fecha_nacimiento) VALUES("
     . ( isset($fecha_nacimiento) && $fecha_nacimiento != '' 
       ? sprintf("'%s'", $fecha_nacimiento)
       : 'null'
       )
     . ")";
    • 0

  3. I ask the question: Do you do that so that in your table the null fields look like this?

    enter image description here

    because that is achieved by defaulting to NULL in the field

    `name` VARCHAR(191) DEFAULT NULL;
    • 0