PHP/Language Basics/Variable Set Unset

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IsSet variable

   <source lang="html4strict">

<? 

  $MyVar="Hello there!";

 If(IsSet($MyVar))
   echo "The variable is set. Its value is $MyVar";

?> 

      </source>


The isset() Function

   <source lang="html4strict">

<html> <head> 

    <title>Isset()</title>

</head> <body> <?php 

    $my_var = 100;
  
    if(isset($my_var)) {
         print("\$my_var is set... the value is " . $my_var);
    }
  
    print("
");
    print(isset($some_var) . "
");
  
    $some_var = "I am set";
    print(isset($some_var) . "
");

?> </body> </html> 

      </source>


UnSet array element

   <source lang="html4strict">

<? 

$A=array(0=>"zzzz", 
         "a"=>"aaa", 
         "b"=>"bbb", 
         "c"=>"ccc");
Unset($A["a"]);
echo $A["a"]

?> 

      </source>


unset() Function

   <source lang="html4strict">

<html> <head> 

    <title>Unset()</title>

</head> <body> <?php 

    $authorJ = "A";
    $authorC = "B";
    $jeremy = &$authorJ;
    $charlie = &$authorC;
  
    print("$authorJ 
");
    unset($jeremy);
    print($authorJ . " or " . $jeremy . "
");
  
    print("$authorC 
");
    unset($charlie);
    unset($authorC);
    print($authorC);

?> </body> </html> 

      </source>


Unset variable

   <source lang="html4strict">

<? 

  $a="Hello there!";
  echo $a
  unset($a);
  echo $a; // Error: there is no variable $a

?> 

      </source>
Источник — «http://wbex.ru/index.php?title=PHP/Language_Basics/Variable_Set_Unset&oldid=895»