Php check if null or false

Check Type and Value of Null in PHP

Compare Null Value With Empty String Using Double and Triple Equals Operator in PHP In PHP, there are various comparison operators. To test if something is empty: empty() returns true if a variable is 0, null, false or an empty string.

PHP Check for NULL

$query = mysql_query("SELECT * FROM tablex"); if ($result = mysql_fetch_array($query))< if ($result['column'] == NULL) < print ""; > else < print ""; > > 

If the values are NOT NULL i still get the uncheked box. Am i doing something wrong from above, shoudnt $result[‘column’] == NULL work?

is_null($result['column']) $result['column'] === NULL 

Make sure that the value of the column is really NULL and not an empty string or 0.

The latter returns an normal array index by integers, whereas the former returns an associative array, index by the field names.

Mysql — PHP Check for NULL, PHP Check for NULL. Ask Question Asked 12 years, 10 months ago. Modified 4 years ago. Viewed 156k times And its checked if the value is not null. It dosent seem to do that.. Hense it always goes into the first if statment – Angel.King.47. Oct 16, 2009 at 5:41. Code sampleis_null($result[‘column’])$result[‘column’] === NULLFeedback

Check Type and Value of Null in PHP

This article will compare and check the PHP null value with values like » , 0 , and false . We will use the double and triple equals operator to demonstrate the differences.

Compare Null Value With Empty String Using Double and Triple Equals Operator in PHP

In PHP, there are various comparison operators. We use the Comparison operators to compare the value between two entities. The double and triple Equals Operators in PHP are most commonly used. There is a simple difference between these two comparison operators. The double equals operator, == compares the value between the two entities. Whereas the triple equals operator, === compares the value, as well as the type between the two entities. We need to know these differences to compare the entities in PHP the way we want.

We can compare a null value with an empty string and watch the differences using these, both comparison operators. For example, create a variable $foo and assign it to an empty string. Then, compare the variable with NULL with the double equals operator using the if condition. Display the message foo is null , if the condition is true. Display the message the condition is false , if the condition is false. Similarly, use the triple equals operator for the same piece of code.

We can see that the first code example returns the true value, and the second returns the false value. The double equals operator compares only the value of empty string and NULL , and the value are equal. But, the triple equals operator compares the value as well as the type of these entities. As the empty string is of string type and NULL is of NULL type, the value returned is false. We can use the gettype() function to check the type.

Compare Null Value With 0 Using Double and Triple Equals Operator in PHP

Here, we will compare NULL with 0 using the double equals and triple equals operator. We know that 0 is an integer. When we compare it with NULL using the double equals operator, the condition will be true as 0 is null. But, integer and NULL are different types. Therefore, using the triple equals operator will run the false condition.

Thus, we learned how the double and triple equals comparison operators work while comparing the null value with 0 .

Compare Null Value With false Using Double and Triple Equals Operator in PHP

We will compare NULL with the false boolean value using the double and triple equals comparison operators. The value of false and NULL are the same; therefore, the true condition is executed using the double equals operator. As false is a boolean value, its type is not the same as NULL , so the false condition is executed.

$foo = false; if($foo == NULL) < echo 'foo is null'; >else

$foo = false; if($foo === NULL) < echo 'foo is null'; >else

PHP Null

Check Type and Value of Null in PHP, We can compare a null value with an empty string and watch the differences using these, both comparison operators. For example, create a variable $foo and assign it to an empty string. Then, compare the variable with NULL with the double equals operator using the if condition. Display the message foo is null, if the condition is …

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

I want to display an error when a variable have a BLANK value or EMPTY or NULL value. for example variable is shown below:

 $mo = strtotime($_POST['MondayOpen']); 

and
var_dump($_POST[‘MondayOpen’]) returns string(0) «».

Now I go with below approach

1. First want to find which type of variable $mo is ?(string or integer or other)
2. Which function is better to find that $mo having no value.

I conduct a test with $mo and got these results

is_int($mo);//--Return nothing is_string($mo); //--Return bool(false) var_dump($mo); //--Return bool(true) var_dump(empty($mo));//--Return bool(true) var_dump($mo==NULL);//--Return bool(true) var_dump($mo=='');//--Return nothing 

Please suggest an optimum and right approach to check the variable integrity

var_dump outputs variables for debugging purposes, it is not used to check the value in a normal code. PHP is loosely typed, most of the time it does not matter if your variable is a string or an int although you can cast it if you need to make sure it is one, or use the is_ functions to check.

To test if something is empty:

empty() returns true if a variable is 0, null, false or an empty string.

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 >

PHP offers a function isset to check if a variable is not NULL and empty to Check if a variable is empty.

To return the type, you can use the PHP function gettype

You can check its type using:

but null and empty are different things, you can check with these functions:

Another way to check if variable has been set is to use the isset construct.

Php : How to check a field have blank/empty/NULL value?, As a side note, you are using == which tests for equality, such as 1 == ‘1’ which would evaluate to true.But when you use === it tests if the types are equal. In my example 1 === ‘1’ will return false, since int is not a String. – Anthony Forloney

PHP check if False or Null

I also get confused how to Check if a Variable is false / null when returned from a function.

When to use empty() and when to use isset() to check the condition ?

For returns from functions, you use neither isset nor empty , since those only work on variables and are simply there to test for possibly non-existing variables without triggering errors.

For function returns checking for the existence of variables is pointless, so just do:

To read about this in more detail, see The Definitive Guide To PHP’s isset And empty .

Checking variable ( a few examples )

if(is_null($x) === true) // null if($x === null) // null if($x === false) if(isset($x) === false) // variable undefined or null if(empty($x) === true) // check if variable is empty (length of 0) 

Isset() checks if a variable has a value including ( False , 0 , or Empty string) , But not NULL. Returns TRUE if var exists; FALSE otherwise.

On the other hand the empty() function checks if the variable has an empty value empty string , 0, NULL ,or False. Returns FALSE if var has a non-empty and non-zero value.

ISSET checks the variable to see if it has been set, in other words, it checks to see if the variable is any value except NULL or not assigned a value . ISSET returns TRUE if the variable exists and has a value other than NULL. That means variables assigned a » «, 0, «0», or FALSE are set, and therefore are TRUE for ISSET.

EMPTY checks to see if a variable is empty. Empty is interpreted as: » » (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), and «$var;» (a variable declared, but without a value in a class.

Isset — PHP check if False or Null, There are a few things to consider that are not mentioned in the existing answers. Use isset to check if a variable has either not been set or has been set to null. Use empty to check if a variable == false. null is cast to false and as with isset, no notice is thrown if the variable has not been set.

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PHP check if False or Null

For returns from functions, you use neither isset nor empty , since those only work on variables and are simply there to test for possibly non-existing variables without triggering errors.

For function returns checking for the existence of variables is pointless, so just do:

Solution 2

Checking variable ( a few examples )

if(is_null($x) === true) // null if($x === null) // null if($x === false) if(isset($x) === false) // variable undefined or null if(empty($x) === true) // check if variable is empty (length of 0) 

Solution 3

Isset() checks if a variable has a value including ( False , 0 , or Empty string) , But not NULL. Returns TRUE if var exists; FALSE otherwise.

On the other hand the empty() function checks if the variable has an empty value empty string , 0, NULL ,or False. Returns FALSE if var has a non-empty and non-zero value.

Solution 4

ISSET checks the variable to see if it has been set, in other words, it checks to see if the variable is any value except NULL or not assigned a value . ISSET returns TRUE if the variable exists and has a value other than NULL. That means variables assigned a » «, 0, «0», or FALSE are set, and therefore are TRUE for ISSET.

EMPTY checks to see if a variable is empty. Empty is interpreted as: » » (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), and «$var;» (a variable declared, but without a value in a class.

Solution 5

isset — Determine if a variable is set and is not NULL

$a = "test"; $b = "anothertest"; var_dump(isset($a)); // TRUE var_dump(isset($a, $b)); // TRUE unset ($a); var_dump(isset($a)); // FALSE 

empty — Determine whether a variable is empty

 // Evaluates as true because $var is set if (isset($var)) < echo '$var is set even though it is empty'; >?> 

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Is a PHP variable NULL or empty?

In this short PHP tutorial, we’re going to check if a variable is null or empty. We’ll first create a function to check for a NULL value, then an empty value, and finally combine both functions for NULL or empty.

In this article

isNull

Let’s start with a basic PHP function to validate whether our variable is NULL . We’ll use isset to check for NULL .

Our isNull function does not return true for empty strings, we’ll have to cater for that also.

isEmpty

Next, we create our isEmpty function.

We simply check for an empty string and return true or false .

isNullOrEmpty

Our final function is a combination of isNull and isEmpty

The function isNullOrEmpty will determine whether a variable is not null or empty.

Key Takeaways

• Our code validates a string variable for null or empty.
• We use a simple if not NULL or empty check to determine whether to return TRUE or FALSE .
• You could update the function to trim the variable before checking for empty.
• Related PHP functions: empty, is_null

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