Passing variables to a PHP extension by reference

Any variable can be passed to a PHP extension by reference. This differs from Java™ where scalar types and object references are always passed by value. This tutorial extends the big decimal extension by adding a new extension function that negates the value passed. The negated value is passed by reference.

1 Add the following Java code to the BigDecimalExtension class:

@XAPIArguments(MandatoryArguments = 1, PassSemantics = { XAPIPassSemantics.ByReference })
@XAPIFunction("negate_bigdecimal")      
public void negate(RuntimeContext ctxt) {
        BigDecimal arg = new BigDecimal(ctxt.getStringArgument(0).getString());           
        BigDecimal result = arg.negate();      
        ctxt.setArgument(0, result.toString());
}

2 Change the sample.php code to exercise the new function.

<?php	
$value = '111111111111111';
negate_bigdecimal($value);
echo "Negated big decimal ".$value;
?>

3 Run the IBM® WebSphere® sMash application and point a Web browser at http://localhost:8080/sample.php

The example uses the _XAPIPassSemantics_ annotation, this tells the PHP runtime to pass the variable by reference instead of by value (which is the default).