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 <html> 

  <head> 

   <title> function_exists.php </title> 

   <meta charset="UTF-8"> 

   <meta name="Author" content=""> 

   <meta name="Keywords" content=""> 

   <meta name="Description" content=""> 

  </head> 



  <body> 

   <?php 

 function add($a=9,&$b=2) 

 { 

return $b=$a + $b; 

 } 

 if(function_exists('add')) 

 { 

echo add() . '<br>'; 

echo add(3) . '<br>'; 

//echo add(3,3) . '<br>'; 

$X=99; 

     echo add(1,$X) . '<br>'; 

     echo $X . '<br>'; 

 } 



 if(function_exists('addxx')) 

 { 

echo 'addxx<br>'; 

 } 



   ?> 



  </body> 
</html>

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