The conjunctions ινα and εαν are usually followed by a verb in the subjunctive mood.
οὗτος ἦλθεν εἰς μαρτυρίαν ἵνα μαρτυρήσῃ περὶ τοῦ φωτός, ἵνα πάντες πιστεύσωσιν δι’ αὐτοῦ.
greek syntax principle 27
The conjunctions ινα and εαν are usually followed by a verb in the subjunctive mood.
οὗτος ἦλθεν εἰς μαρτυρίαν ἵνα μαρτυρήσῃ περὶ τοῦ φωτός, ἵνα πάντες πιστεύσωσιν δι’ αὐτοῦ.