Difference between call by value and call by reference in PHP
Call by value means passing the value directly to a function. The called function uses the value in a local variable; any changes to it do not affect the source variable.
Call by reference means passing the address of a variable where the actual value is stored. The called function uses the value stored in the passed address; any changes to it do affect the source variable.
Example
This is a "global", or automatic global, variable. This simply means that it is available in all scopes throughout a script. There is no need to do global $x; to access it within functions or methods.
<?php
//Call by value program
function abc($x)
{
$x=$x+10;
return($x);
}
$a=20;
echo abc($a)."<br>";
echo ($a);
?>
Note: Call by value: in the call by value method, the called function creates a new set of variables and copies the values of arguments into them.
Output:
![Call by value program in php.jpg]()
<?php
//call by reference program in php
function abc($x)
{
$x=$x-10;
return($x);
}
$a=50;
echo abc($a)."<br>";
echo ($a);
?>
Note: Call by reference: in the call by reference method, instead of passing a value to the function being called a reference/pointer to the original variable is passed.
Output:
![Call by reference program in php.jpg]()