If you are new to PHP or just need to refresh your skills, this is the place to start. This series of tutorials will give you the basic knowledge you will need to create a simple PHP website.

PHP is a reflective programming language originally designed for producing dynamic web pages.[1] PHP is used mainly in server-side scripting, but can be used from a command line interface or in standalone graphical applications. Textual User Interfaces can also be created using ncurses.

PHP Manual
Prev	Chapter 21. References Explained	Next

Passing by Reference

You can pass variable to function by reference, so that function could modify its arguments. The syntax is as follows:


<?php
function foo(&$var)
{
    $var++;
}

$a=5;
foo($a);
// $a is 6 here
?>

Note that there's no reference sign on function call - only on function definition. Function definition alone is enough to correctly pass the argument by reference. In recent versions of PHP you will get a warning saying that "Call-time pass-by-reference" is deprecated when you use a & in foo(&$a);.

The following things can be passed by reference:

Variable, i.e. foo($a)
New statement, i.e. foo(new foobar())
Reference, returned from a function, i.e.:
<?php function &bar() { $a = 5; return $a; } foo(bar()); ?>
See also explanations about returning by reference.

Any other expression should not be passed by reference, as the result is undefined. For example, the following examples of passing by reference are invalid:


<?php
function bar() // Note the missing &
{
    $a = 5;
    return $a;
}
foo(bar()); // Produces fatal error since PHP 5.0.5

foo($a = 5); // Expression, not variable
foo(5); // Produces fatal error
?>

These requirements are for PHP 4.0.4 and later.

Prev	Home	Next
What References Are Not	Up	Returning References

You Are At PHP: Passing by Reference - Manual Area

Passing by Reference