PHP destructor and garbage collection mechanism

WBOY
Release: 2016-07-25 08:53:50
Original
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  1. class person{
  2. public function __destruct() {
  3. echo "
    The destructor is executed here";
  4. echo "
    This is generally used Place, close the database, close the file, etc. finishing work ";
  5. }
  6. }
  7. $p = new person();
  8. for ($i = 0; $i < 5; $i++) {
  9. echo "< br /> $i";
  10. }
  11. //The object is destroyed before the php program ends.
  12. ?>
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When the object is not pointed to, the object is destroyed.

  1. class person {
  2. public function __destruct() {
  3. echo "
    The destructor is executed here";
  4. echo "
    Generally used here To place, close the database, close the file, etc. ";
  5. }
  6. }
  7. $p = new person();
  8. $p = null;
  9. //We see here that the destructor is executed here. .
  10. for ($i = 0; $i < 5; $i++) {
  11. echo "
    $i";
  12. }
  13. ?>
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Set $p Assign $p a string if it is empty or on line 11, so that the object pointed to by $p becomes a garbage object. PHP will garbage destroy this object.

unset variable

  1. class person {
  2. public function __destruct() {
  3. echo "
    The destructor is executed here
    ";
  4. }
  5. }
  6. $ p = new person();
  7. $p1 = $p; //Set the new reference variable $p1 to also point to this object
  8. unset($p);
  9. echo "Do you see that /$p is destroyed and the object is also destroyed? What?";
  10. for ($i = 0; $i < 5; $i++) {
  11. echo "
    $i";
  12. }
  13. unset($p1);
  14. echo "We see Here, the destructor is executed";
  15. ?>
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When unset a reference variable, unset destroys the variable pointing to the object, not the object.



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