`is_null` is the same as `=== null`.  Both return true when a variable is `null` (or unset).

Note that I&#39;m using `===` and not `==`.  `===` compares type as well as value.

So you can understand it better:

    $a = null;
    $b = 0;
    
    is_null($a) // TRUE
    $a == null  // TRUE
    $a === null // TRUE
    is_null($b) // FALSE
    $b == null  // TRUE
    $b === null // FALSE

There are a couple really good charts on the php.net site that show how different values react:

[Type Comparison - php.net][1]


  [1]: http://php.net/manual/en/types.comparisons.php

You can check the comparison between **is_null()** and **null === $var**

[Good comparison between two][1]


  [1]: http://hakre.wordpress.com/2011/03/29/php-is_null-vs-null/

`===null` is recommended by Rasmus Lerdorf, the inventor of PHP. 
Rasmus says the test for null is faster than the test of `isset`. His recommendation is sufficient reason to look at the difference seriously. The difference would be significant if you had a small loop going through the same code thousands of times in the one Web page request.

UPD: Some speed test for is_null and strict comparison:
```
PHP 5.5.9
is_null - float(2.2381200790405)
===     - float(1.0024659633636)

PHP 7.0.0-dev
is_null - float(1.4121870994568)
===     - float(1.4577329158783)
```

`==` doesn&#39;t check the type, so somehow, somewhere, something like the string `&#39;&#39;` or the string `&#39;null&#39;` may come up as equal to null.

Use triple equals sign, `===`, to not only check two values are equal but also that they are of the same type.

I&#39;m working with fulltext, I executed an command to add the fulltext index to multiple comments, and returned no errors, then I did:

    SELECT * FROM products WHERE MATCH(`brand`) AGAINST(&#39;Skoda&#39;);

Which is in the brand column - but I get following:

&gt; Can&#39;t find FULLTEXT index matching the column list

Eventho, when my table looks like this:

    FULLTEXT KEY `name` (`name`,`breadcrumb`,`description`,`brand`,`price`,`year`,`km`,`usage`,`type`)

Is it because I should use the `name` instead? to do the search? Or what can be wrong.

Can&#39;t find FULLTEXT index matching the column list (indexes is set)

Lets try to explain my question:
I got an application and a service.
The application is started with activity A.
The service sends a broadcast that will let the application start Activity B
Now the user starts activity C.

Now the service wants to start activity B again. But how do I let him know that the activity is still on the stack, or is there an intent flag for this?

How do I avoid that it will launch activity B because its already in the stack?

Android: How do I avoid starting activity which is already in stack?

In PHP, what is the difference between `is_null` and `==null` in PHP? What are the qualifications for both to return true?

PHP is_null() and ==null

<p>In PHP, what is the difference between <code>is_null</code> and <code>==null</code> in PHP? What are the qualifications for both to return true?</p>


In PHP to check non-equality (without checking type) you can do this:

    if( A != B ) {
        DO SOMETHING;
    }

But you can also do this, which has the same result:

    if( A &lt;&gt; B ) {
        DO SOMETHING;
    }

Is there any difference?

Does using `!=` over `&lt;&gt;` change the evaluation in any way, shape, or form?

What is the difference between &lt;&gt; and !=

I keep getting the error alert. There is nothing wrong with the MYSQL part, the query gets executed and I can see the email addresses in the db.

**The client side:**

    &lt;script type=&quot;text/javascript&quot;&gt;
      $(function() {
        $(&quot;form#subsribe_form&quot;).submit(function() {
          var email = $(&quot;#email&quot;).val();
    
          $.ajax({
            url: &quot;subscribe.php&quot;,
            type: &quot;POST&quot;,
            data: {email: email},
            dataType: &quot;json&quot;,
            success: function() {
              alert(&quot;Thank you for subscribing!&quot;);
            },
            error: function() {
              alert(&quot;There was an error. Try again please!&quot;);
            }
          });
          return false;
        });
      });
    &lt;/script&gt;

**The server side:**

    &lt;?php 
    $user=&quot;username&quot;;
    $password=&quot;password&quot;;
    $database=&quot;database&quot;;
    
    mysql_connect(localhost,$user,$password);
    mysql_select_db($database) or die( &quot;Unable to select database&quot;);
    
    $senderEmail = isset( $_POST[&#39;email&#39;] ) ? preg_replace( &quot;/[^\.\-\_\@a-zA-Z0-9]/&quot;, &quot;&quot;, $_POST[&#39;email&#39;] ) : &quot;&quot;;
    
    if($senderEmail != &quot;&quot;)
    	$query = &quot;INSERT INTO participants(col1 , col2) VALUES (CURDATE(),&#39;&quot;.$senderEmail.&quot;&#39;)&quot;;
    mysql_query($query);
    mysql_close();
    
    $response_array[&#39;status&#39;] = &#39;success&#39;;    
    
    echo json_encode($response_array);
    ?&gt;

How do I return a proper success/error message for JQuery .ajax() using PHP?

I have a `php` application where I want to read data from excel, Insert into database and then generate pdf reports for specific users.
I searched a lot but nothing specific given about both things.


How to use phpexcel to read data and insert into database?

How would I get the first letter of each word for a given string?

    $string = &quot;Community College District&quot;;
    $result = &quot;CCD&quot;;

I found the javascript method but wasn&#39;t sure how to convert it to php.

Get the first letter of each word in a string

I love the null-coalescing operator because it makes it easy to assign a default value for nullable types.

     int y = x ?? -1;

That&#39;s great, except if I need to do something simple with `x`. For instance, if I want to check `Session`, then I usually end up having to write something more verbose.

I wish I could do this:

    string y = Session[&quot;key&quot;].ToString() ?? &quot;none&quot;;

But you can&#39;t because the `.ToString()` gets called before the null check so it fails if `Session[&quot;key&quot;]` is null. I end up doing this:

    string y = Session[&quot;key&quot;] == null ? &quot;none&quot; : Session[&quot;key&quot;].ToString();

It works and is better, in my opinion, than the three-line alternative:

    string y = &quot;none&quot;;
    if (Session[&quot;key&quot;] != null)
        y = Session[&quot;key&quot;].ToString();

Even though that works I am still curious if there is a better way. It seems no matter what I always have to reference `Session[&quot;key&quot;]` twice; once for the check, and again for the assignment. Any ideas?

What is the proper way to check for null values?

I&#39;m trying to select the max date in three different fields in each record (MySQL)
So, in each row, I have date1, date2 and date3: date1 is always filled, date2 and date3 can be NULL or empty
The GREATEST statement is simple and concise but has no effects on NULL fields, so this doesn&#39;t work well:

    SELECT id, GREATEST(date1, date2, date3) as datemax FROM mytable

I tried also more complex solutions like this:

    SELECT
        CASE
            WHEN date1 &gt;= date2 AND date1 &gt;= date3 THEN date1
            WHEN date2 &gt;= date1 AND date2 &gt;= date3 THEN date2
            WHEN date3 &gt;= date1 AND date3 &gt;= date2 THEN date3
            ELSE                                        date1
        END AS MostRecentDate

Same problem here: NULL values are a GREAT problem in returning the right records

Please, have you got a solution?
Thanks in advance....



MySQL: get MAX or GREATEST of several columns, but with NULL fields

I know how to check if a parameter is null but i am not sure how to check if its empty ... I have these parameters and I want to check the previous parameters are empty or null and then set them like below

    ALTER PROCEDURE [dbo].[GetSummary]
        @PreviousStartDate NVARCHAR(50) ,
        @PreviousEndDate NVARCHAR(50) ,
        @CurrentStartDate NVARCHAR(50) ,
        @CurrentEndDate NVARCHAR(50)
    AS
      BEGIN
        IF(@PreviousStartDate IS NULL OR EMPTY)
            SET @PreviousStartdate = &#39;01/01/2010&#39;  for example..

I would appreciate the help.




Check if a parameter is null or empty in a stored procedure

I was interviewing a guy for a mid-level software engineering position yesterday, and he mentioned that in C, NULL is not always zero and that he had seen implementations of C where NULL is not zero. I find this highly suspect, but I want to be sure. Anyone know if he is right? 

(Responses will not affect my judgement on this candidate, I&#39;ve already submitted my decision to my manager.)

Is NULL always zero in C?

Imagine I have a class Family. It contains a List of Person. Each (class) Person contains a (class) Address. Each (class) Address contains a (class) PostalCode.  Any &quot;intermediate&quot; class can be null. 

So, is there a simple way to get to PostalCode without having to check for null in every step? i.e., is there a way to avoid the following daisy chaining code? I know there&#39;s not &quot;native&quot; Java solution, but was hoping if anyone knows of a library or something. (checked Commons &amp; Guava and didn&#39;t see anything)

    if(family != null) {
        if(family.getPeople() != null) {
            if(family.people.get(0) != null) {
                if(people.get(0).getAddress() != null) {
                    if(people.get(0).getAddress().getPostalCode() != null) {
                        //FINALLY MADE IT TO DO SOMETHING!!!
                    }
                }
            }
        }
    }

No, can&#39;t change the structure. It&#39;s from a service I don&#39;t have control over. 

No, I can&#39;t use Groovy and it&#39;s handy &quot;Elvis&quot; operator. 

No, I&#39;d prefer not to wait for Java 8 :D

I can&#39;t believe I&#39;m the first dev ever to get sick &#39;n tired of writing code like this, but I haven&#39;t been able to find a solution. 

Content Type	Original Author	Original Content on Stackoverflow
Question	kel_ff0080	View Question on Stackoverflow
Solution 1 - Php	Rocket Hazmat	View Answer on Stackoverflow
Solution 2 - Php	Daniel Ribeiro	View Answer on Stackoverflow
Solution 3 - Php	keithhatfield	View Answer on Stackoverflow
Solution 4 - Php	Umut KIRGÖZ	View Answer on Stackoverflow
Solution 5 - Php	Achim Krauß	View Answer on Stackoverflow
Solution 6 - Php	DanRedux	View Answer on Stackoverflow

PHP is_null() and ==null

Php Problem Overview

Php Solutions

Solution 1 - Php

Solution 2 - Php

Solution 3 - Php

Solution 4 - Php

Solution 5 - Php

Solution 6 - Php

Android: How do I avoid starting activity which is already in stack?

Can't find FULLTEXT index matching the column list (indexes is set)

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