What does ‘<?=’ short open tag mean in PHP ?

The <?php is used to identify the start of a PHP document.

In PHP whenever it reads a PHP document, It looks for:

<?php ?> 

It process the codes in between the above tags only and leaves the other codes around them.

For example :

<?php 
    echo "Hello PHP !"; 
?> 

Output :

Hello PHP !

Note : But a special case is when you write a PHP file the end tag can be omitted, Only the start tag is needed.

The below code works fine as well:

<?php 
   echo "Hello PHP !"; 

Output:

Hello PHP !

The <= tag is called short open tag in PHP. To use the short tags, one must have to enable it from settings in the PHP.ini file.

First of all ensure that short tags are not disabled, To check it, go into php.ini file On line 77 .

(location in linux systems :/etc/php5/apache2/php.ini)

Find the below line in the file and add (On) instead of (Off):

short_open_tag=On

However, from PHP version 5.4.0, the short tags are available for use regardless of the settings in the PHP.ini file.

The below two examples produces the same output with and without short open tags.

Example 1 : Normal Way.

<?php 
    $username = "Codegyan"; 
    echo "$username"; 
?> 

Output:

Codegyan

Example 2 : The Short Hand Way.

<?php 
    $username = "Codegyan"; 
?> 
<?= $username ?> 

Output:

Codegyan

As you can observe, both of the above codes gives us the same output. So, using short tags we told to php interpreter that:

<? ?> can be treated same as <?php ?>

The above example can be further modified as follows :

<?= 
   $username = "Codegyan"; 
?> 

Output:

Codegyan