How to delete a variable in php

In PHP, you can use the unset() function to delete a variable. This function is used to destroy a given single or multiple variables. The syntax format is "unset (variable to be destroyed)". The behavior of unset() within a function will vary depending on the type of variable you want to destroy.

The operating environment of this tutorial: Windows 7 system, PHP version 7.1, DELL G3 computer

The unset() function is a built-in function in PHP Function used to destroy the given variable (release the given variable).

The unset function can destroy a single variable, multiple variables, arrays, etc. at the same time.

The behavior of unset() in a function will vary depending on the type of variable you want to destroy. If the function is called from inside any user-defined function, then it will unset the value associated with the internal variable, leaving the initialized value outside.

This means that this function only sets local variables. If we want to unset a global variable in a function, then we have to do it using the $GLOBALS array.

Syntax format:

unset($var)

Parameter description:

• $var: This parameter is required and is a variable to be destroyed.

Return value

• There is no return value.

Example 1:

<?php
// 销毁单个变量
unset ($foo);
 
// 销毁单个数组元素
unset ($bar[&#39;quux&#39;]);
 
// 销毁一个以上的变量
unset($foo1, $foo2, $foo3);
?>

Example 2:

<?php
  $var = "hello";
  // 外部不会反映任何变化
  function unset_value()
  {
      unset($var);
  }
    
  unset_value();
  echo $var;
?>

Output:

hello

Example 3:

<?php
     
      $var = "hello";
        
      // Change would be reflected outside the function 
      function unset_value()
      {
          unset($GLOBALS[&#39;var&#39;]);
      }
        
      unset_value();
      echo $var;
?>

Output:

No Output

Example 4:

<?php
      
      // user-defined function
      function unset_value()
      {
          static $var = 0;
          $var++;
            
          echo "Before unset:".$var." ";
            
          unset($var);
      
          // This will create a new variable with
          // existing name
          $var = 5;
           
          echo "After unset:".$var."\n";          
      }
        
      unset_value();
      unset_value();
      unset_value();
      unset_value();
        
?>

Output:

Before unset:1 After unset:5
Before unset:2 After unset:5
Before unset:3 After unset:5
Before unset:4 After unset:5

Note: If a variable is declared static and not set inside a function, the effect will only be in the rest of the context of the function. The above call outside the function will restore this value.

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