How can you pass a variable by reference in PHP?

By using an ampersand (&) sign in-front of the variable, we can pass the variable by reference.

Why or when to use variable by reference ?

When PHP function arguments are passed by value, and value is changed within function, it does not change variable value outside the function. To allow a function to modify its argument value outside the function, they must be passed by reference.

Example:

<?php
function add_line(&$line)
{
    $line.= 'and extra words added.';
}
 
$sample_line= 'This is a sample line, ';
add_line($sample_line);
echo $sample_line;    // outputs 'This is a sample line,  and extra words added.'
?>

If we do not use value by reference (&), then the output will be: ‘This is a sample line,’


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