PHP Is Null When Empty

php is null when empty?

What you're looking for is:

if($variable === NULL) {...}

Note the ===.

When use ==, as you did, PHP treats NULL, false, 0, the empty string, and empty arrays as equal.

How to validate null or empty in php

You can validate in many ways :

1. By using following php variable handling functions

   • is_null(mixed $var)
   • isset(mixed $var)
   • empty(mixed $var)

2. By using comparison operator ==, === or !=

is_null(mixed $var)

You can use php variable handling function is_null(mixed $var) which returns TRUE if var is null, otherwise FALSE.

<?php
 $foo = NULL;
 $bar = 'NULL';
 var_dump(is_null($foo), is_null($bar));
?>

OUTPUT

bool(true) bool(false)

---

As you can see $bar = 'NULL' and $bar = NULL both are different thing. Actually, in one it is initializing with a string, not with NULL.

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isset(mixed $var)

It returns TRUE if var exists and has value other than NULL, FALSE otherwise.

Note

isset() only works with variables as passing anything else will result in a parse error. For checking if constants are set use, the defined() function.

<?php
     $foo = NULL;
     $bar = 'NULL';
     var_dump(isset($foo), isset($bar));
?>

OUTPUT

bool(false) bool(true)

---

empty(mixed $var)

Returns FALSE if var exists and has a non-empty, non-zero value. Otherwise returns TRUE.

<?php
     $foo = NULL;
     $bar = 'NULL';
     var_dump(empty($foo), empty($bar));
?>

OUTPUT

bool(true) bool(false)

---

== or === or !=

You can use comparison operator ==, === or != to check whether a variable is null or not.

   <?php
     $foo = NULL;
     $bar = 'NULL';

// Using == operator   
     echo "Using '==' operator\n";
     if($foo == NULL)

    echo "foo is NULL\n";

     else

    echo "foo is not NULL\n";

     if($bar == NULL)

    echo "bar is NULL\n";

     else

    echo "bar is not NULL\n";

// Using === operator 
     echo "\nUsing '===' operator\n";
     if($foo === NULL)

    echo "foo is NULL\n";

     else

    echo "foo is not NULL\n";

     if($bar === NULL)

    echo "bar is NULL\n";

     else

    echo "bar is not NULL\n";

?>

OUTPUT

Using '==' operator
foo is NULL
bar is not NULL

Using '===' operator
foo is NULL
bar is not NULL

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The only difference between == and === is that == just checks to see if the left and right values are equal. But, the === operator (note the extra “=”) actually checks to see if the left and right values are equal and also checks to see if they are of the same variable type (like whether they are both booleans, ints, etc.).

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Check for NULL or empty '' in function?

If you just check for the value of the variable you will get true whether null or an empty string (''):

null == ''; // 1 (true)

You also need to check for type:

null === ''; // (false)

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So instead of:

if( $a != NULL )

Run:

if( $a !== NULL )

Which will also check for type; '' is a string - not null type.

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Rearranged function:

function title($a = NULL, $b = NULL, $c = NULL) {
    if( $a !== NULL )
    {
        echo 'A1';
        if( $a !== '' )
        {
            echo 'A2';
        }
    }
    if( $b !== NULL )
    {
        echo 'B1';
        if( $b !== '' )
        {
            echo 'B2';
        }
    }
    if( $c !== NULL )
    {
        echo 'C1';
        if( $c !== '' )
        {
            echo 'C2';
        }
    }
}

title(NULL, '', 'C'); // outputs: B1C1C2

Make a value into NULL instead of empty in php

It's a normal problem with null-able strings. For a quick solution, you can change your code to:

$code = NULL;
if( !empty($_FILES['logo']['name']) ){
 ...
}

For more details, you can check this question:
MySQL and PHP - insert NULL rather than empty string

php : How to check a field have blank/empty/NULL value?

doing strtotime will return false if it cannot convert to a time stamp.

$mo = strtotime($_POST['MondayOpen']);
if ($mo !== false)
{
//valid date was passed in  and $mo is type int
}
else
{
//invalid date let the user know
}

What is the difference between null and empty?

A variable is NULL if it has no value, and points to nowhere in memory.

empty() is more a literal meaning of empty, e.g. the string "" is empty, but is not NULL.

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)

Source.

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Example

$a is NULL.

$a = '' is empty, but not NULL.

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Update

If $a='' is empty but not NULL, when do I use the empty() function and when do I use the isset() function.

isset() will return FALSE is the variable is pointing to NULL.

Use empty() when you understand what is empty (look at the list above).

Also when you say it points nowhere in memory, what does that mean exactly?

It means that $str = '' will be in memory as a string with length of 0.

If it were $str = NULL, it would not occupy any memory.

PHP: insert NULL if input value is empty

You can try this way:

remove single invated comma from query and set them to query it will surely work for you

if (empty($_POST['caller'])){ 
    $caller="NULL";
}else{ 
    $caller=mysqli_real_escape_string($con, $_POST['caller']);
    $caller="'$caller'";
}

$sql_caller = "INSERT INTO `tblcall_info` VALUES ('','$save_inc_id','$call_time','$call_date','$caller','$caller_contact','$receiver','$device')";

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