& use of

<?php
function example( &$m ){ //Define a function and pass the variable
$m of the parameter $m = $m * 5 + 10;
echo "In the function: \$m = ".$m; / /Output the value of the parameter
}
$m = 1;
example( $m ) ; //Pass by value: pass the value of $m to the parameter $m
echo "<p>Outside the function: \$m = $m < p>" ; //The value of the actual parameter changes, output m=15
?>