Function to Make Empty String NULL for MySQL Insertion in PHP

Question

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;

What am I doing wrong? Also should I call the function before escaping?

psx · Accepted Answer · 2011-10-13 14:15:49Z

2

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

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

answered Oct 13, 2011 at 14:15

psx

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2 Comments

Kamil Sindi Over a year ago

I tried that but have the same problem. Can I just call the function, e.g. IsEmptyString($name) or do I have to set $name = IsEmptyString($name).

psx Over a year ago

You need to call $name = IsEmptyString($name). Another option is to define the function as: function IsEmptyString(&$val) then you do not need to return the value

Mob · Accepted Answer · 2011-10-13 14:16:58Z

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.

roselan · Accepted Answer · 2011-10-13 14:19:34Z

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;

martinstoeckli · Accepted Answer · 2011-10-13 14:36:48Z

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'; }

@Rufinus - It seems that the OP is using the string 'NULL' to build an SQL statement. The function is a modification of the given example, it has other flaws too, as a misleading name for example.

Nathan Arthur · Accepted Answer · 2016-10-17 14:05:03Z

Looks like a good candidate for a ternary operator:

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

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