PHP/MYSQL: check if variable is empty

Question

I want to prevent an empty value from going into a MySQL database

I'm using following but for some reason it is letting the empty values get through...

if (trim($var)= '' || !isset($var)){
header("Location:page.php?er=novariablel");
}
else {
...insert into database
}

Note, there is a bunch of complicated stuff that sets the value of var which is why I want to have both the ='' and the !isset because either might be the case.

Am I missing something with the or statement, i.e. it evaluates to false if both are true. Or what am I doing wrong?

Fabrício Matté · Accepted Answer · 2012-05-18 02:54:29Z

5

You're lacking an = for your Equal Comparison Operator inside your if statement. Try:

if (trim($var) == '' || !isset($var)){

answered May 18, 2012 at 2:54

Fabrício Matté

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2 Comments

Fabrício Matté Over a year ago

No problem, just keep in mind to use == or === equality operators inside your conditional statements in future, otherwise you'll run in the same problem again. :)

mickmackusa Over a year ago

Calling trim() before isset() doesn't make sense. If the variable isn't declared, then trim() will complain. If the variable is declared, then isset() is inappropriate.

Community · Accepted Answer · 2023-11-17 20:38:18Z

3

Try:

if (!isset($var) || empty(trim($var))){

empty() is a better way to check to see if a variable has no value. Just keep in mind that the following will return true:

The following things are considered to be empty:

"" (an empty string)
0 (0 as an integer)
0.0 (0 as a float)
"0" (0 as a string)
NULL
FALSE
array() (an empty array)
var $var; (a variable declared, but without a value in a class)

edited Nov 17, 2023 at 20:38

CommunityBot

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answered May 18, 2012 at 2:52

John Conde

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Comments

Sudhir Bastakoti · Accepted Answer · 2012-05-18 02:53:25Z

0

Try:

$var = trim($var);
if (!empty($var)){
  //not empty
}

answered May 18, 2012 at 2:53

Sudhir Bastakoti

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1 Comment

mickmackusa Over a year ago

trim() before an empty() call doesn't make sense. If the variable isn't declared, then trim() will complain. If the variable is declared, then empty() is doing too much.

sumit · Accepted Answer · 2012-05-18 02:56:26Z

0

Try

if (strlen(trim($var)))==0

answered May 18, 2012 at 2:56

sumit

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Comments

geekoraul · Accepted Answer · 2012-05-18 03:53:37Z

0

You should also have put a constraint in your database table attribute that it will not accept NULL values. Then your entry would have not been made in the database.

answered May 18, 2012 at 3:53

geekoraul

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Comments

Andrew · Accepted Answer · 2012-06-03 01:33:46Z

0

@John this is great advice.

empty(trim($var))

I've been programming for 6 years and I never thought of trimming the variable before checking to see if it's empty.

answered Jun 3, 2012 at 1:33

Andrew

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1 Comment

mickmackusa Over a year ago

This answer is not good advice. If $var isn't declared, then trim() will complain. If $var is declared, then empty() is doing too much.

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