Are there pointers in php

Question

What does this code mean  Is this how you declare a pointer in php    this- gt entryId    entryId

User · Answer

entryId is an instance property of the current class   this  And  entryId is a local variable

User · Answer

Variable names in PHP start with   so  entryId is the name of a variable   this is a special variable in Object Oriented programming in PHP  which is reference to current object  -  is used to access an object member  like properties or methods  in PHP  like the syntax in C    so your code means this   Place the value of variable  entryId into the entryId field  or property  of this object   The  amp  operator in PHP  means pass reference  Here is a example    b 2   a  b   a 3  print  a  print  b     output is 32   b 2   a  amp  b     note the  amp  operator  a 3  print  a  print  b     output is 33   In the above code  because we used  amp  operator  a reference to where  b is pointing is stored in  a  So  a is actually a reference to  b   In PHP  arguments are  passed by value by default  inspired by C   So when calling a function  when you pass in your values  they are copied by value not by reference  This is the default IN MOST SITUATIONS  However there is a way to have pass by reference behaviour  when defining a function  Example   function plus by reference   amp  param              what ever you do  will affect the actual parameter outside the function        param        a 2  plus by reference   a    echo  a     output is 3   There are many built-in functions that behave like this  Like the sort   function that sorts an array will affect directly on the array and will not return another sorted array   There is something interesting to note though  Because pass-by-value mode could result in more memory usage  and PHP is an interpreted language  so programs written in PHP are not as fast as compiled programs   to make the code run faster and minimize memory usage  there are some tweaks in the PHP interpreter  One is lazy-copy  I m not sure about the name   Which means this   When you are coping a variable into another  PHP will copy a reference to the first variable into the second variable  So your new variable  is actually a reference to the first one until now  The value is not copied yet  But if you try to change any of these variables  PHP will make a copy of the value  and then changes the variable  This way you will have the opportunity to save memory and time  IF YOU DO NOT CHANGE THE VALUE   So    b 3   a  b      a points to  b  equals to  a  amp  b  b 4     now PHP will copy 3 into  a  and places 4 into  b   After all this  if you want to place the value of  entryId into  entryId  property of your object  the above code will do this  and will not copy the value of entryId  until you change any of them  results in less memory usage  If you actually want them both to point to the same value  then use this    this- gt entryId  amp  entryId

User · Answer

PHP passes Arrays and Objects by reference  pointers   If you want to pass a normal variable Ex   var    boo   then use  boo    amp  var

User · Answer

No  As others said   quot There is no Pointer in PHP  quot  and I add  there is nothing RAM related in PHP  And also all answers are clear  But there were points being left out that I could not resist  There are number of things that acts similar to pointers  eval construct  my favorite and also dangerous   GLOBALS variable Extra     sign Before Variables  Like prathk mentioned  References   First one At first I have to say that PHP is really powerful language  knowing there is a construct named  quot eval quot   so you can create your PHP code while running it   really cool   although there is the danger of PHP Injection which is far more destructive that SQL Injection  Beware  example  Code   a  echo  quot Hello World  quot     eval   a    Output  Hello World   So instead of using a pointer to act like another Variable  You Can Make A Variable From Scratch   Second one  GLOBAL variable is pretty useful  You can access all variables by using its keys  example  Code   three  quot Hello quot   variable  quot  Amazing  quot   names  quot World quot    arr   Array  quot three quot   quot variable quot   quot names quot    foreach  arr as  VariableName      echo  GLOBALS  VariableName    Output  Hello Amazing World  Note  Other superglobals can do the same trick in smaller scales   Third one You can add as much as    s you want before a variable  If you know what you re doing  example  Code   a  quot b quot    b  quot c quot    c  quot d quot    d  quot e quot    e  quot f quot    echo  a  quot - quot   echo   a  quot - quot       Same as  b echo    a  quot - quot      Same as   b or  c echo     a  quot - quot     Same as    b or   c or  d echo      a       Same as     b or    c or   d or  e  Output  b-c-d-e-f   Last one Reference are so close to pointers  but you may want to check this link for more clarification  example 1  Code   a  quot Hello quot    b  amp  a   b  quot yello quot   echo  a   Output  yello  example 2  Code  function junk  amp  tion    GLOBALS  a      amp  tion    a  quot -Hello World lt br gt  quot    b  quot -To You As Well quot   echo  a  junk  b   echo  a   Output  -Hello World -To You As Well  Hope It Helps

User · Answer

Yes there is something similar to pointers in PHP but may not match with what exactly happens in c or c    Following is one of the example    a    test    b    a   echo  a  echo  b  echo   b     output test a test   This illustrates similar concept of pointers in PHP

User · Answer

That syntax is a way of accessing a class member  PHP does not have pointers  but it does have references    The syntax that you re quoting is basically the same as accessing a member from a pointer to a class in C    whereas dot notation is used when it isn t a pointer

User · Answer

To answer the second part of your question - there are no pointers in PHP    When working with objects  you generally pass by reference rather than by value - so in some ways this operates like a pointer  but is generally completely transparent    This does depend on the version of PHP you are using

User · Answer

PHP can use something like pointers    y array  amp  x     Now  y acts like a pointer to  x and  y 0  dereferences a pointer   The value array  amp  x  is just a value  so it can be passed to functions  stored in other arrays  copied to other variables  etc  You can even create a pointer to this pointer variable   Serializing it will break the pointer  however

User · Answer

You can simulate pointers to instantiated objects to some degree   class pointer      var  child      function pointer  amp  child            this- gt child    child           public function   call  name   arguments           return call user func array             array  this- gt child   name    arguments            Use like this    a   new ClassA      p   new pointer  a     If you pass  p around  it will behave like a C   pointer regarding method calls  you can t touch object variables directly  but that s evil anyways

[php] Are there pointers in php?

Examples related to php

Examples related to pointers