Function to Make Empty String NULL for MySQL Insertion in PHP

This is similar question to MySQL and PHP - insert NULL rather than empty string but I'm still encountering the problem.

I'm trying to create a function so that an empty string is inserted as a NULL into MySQL.

I create the function IsEmptyString:

function IsEmptyString($val){
    if (trim($val) === ''){$val = "NULL";}
}

Before inserting the the variable, I escape it and then I call the function above. I've also tried $val = NULL;

W开发者_JAVA百科hat am I doing wrong? Also should I call the function before escaping?

You need to return $val at the end of the function:

function IsEmptyString($val){
    if (trim($val) === ''){$val = "NULL";}
    return $val;
}

You're not returning the value. This should work

function IsEmptyString($val){
    if (trim($val) === ''){$val = "NULL";}
return $val;
}

Also you're assigning your variable to a string and not null.

This line $val = "NULL";

should be

$val = null;

Also see PHP's isset() and empty() functions.

alternativly, you can pass val as reference.

function IsEmptyString(&$val){
    if (trim($val) === ''){$val = "NULL";}
}

however, be carefull not to send "'".$val."'" to the database;

Either you can return the result with return...

function IsEmptyString($val)
{
  if (trim($val) === '')
    return 'NULL';
  else
    return $val;
}

...or you have to pass the variable as reference (note the & before the $val)

function IsEmptyString(&$val)
{
  if (trim($val) === '')
    $val = 'NULL';
}

Looks like a good candidate for a ternary operator:

function valOrNull($val) {
    return (trim($val) === '') ? NULL : $val;
}