Conditional subpatterns

Conditional subpatterns

Conditional subpatterns are a particular type of non capturing subpattern that implement an if-then-else syntax structure. In REBuilder conditional subpatterns are represented by the REBuilder\Pattern\ConditionalSubpattern class.

The classes that represent the parts that compose the conditional subpattern are:

• REBuilder\Pattern\Assertion: the "if" part is an assertion that can be implemented as described in Assertions page and can be added using addAssertion.
• REBuilder\Pattern\ConditionalThen: the "then" part is a container that can be added using addConditionalThen.
• REBuilder\Pattern\ConditionalElse: the optional "else" part is a container that can be added using addConditionalElse.

Example:

• Match "a"
• If followed by "c" match "c"
• Otherwise match "d"

$regex
      ->addCharAndContinue("a")             //Add "a"
      ->addConditionalSubPattern()          //Start the conditional subpattern
            ->addAssertion()                //Add the "if" assertion
                  ->addCharAndContinue("c") //Match "c"
            ->getParent()                   //Back to the conditional subpattern
            ->addConditionalThen()          //Add the "then" part
                  ->addCharAndContinue("c") //Match "c"
            ->getParent()                   //Back to the conditional subpattern
            ->addConditionalElse()          //Add the "else" part
                  ->addCharAndContinue("d");//Match "d"

echo $regex; // "/a(?(?=c)c|d)/"

If you don't want to use the "chain" syntax to create the regex you can also use some shortcut methods to add every part: setIf, setThen, setElse. These methods accept an instance of the classes listed above. You can also use getters method getIf, getThen and getElse to access every part of the conditional subpattern.