PSBT\Creator, compute length before loop

PSBT: fix phpdoc for function returning unknown key/values

src/Transaction/PSBT/Creator.php

@@ -10,15 +10,16 @@ class Creator
 {
     public function createPsbt(TransactionInterface $tx, array $unknowns = []): PSBT
     {
+        $nIn = count($tx->getInputs());
         $inputs = [];
-        for ($i = 0; $i < count($tx->getInputs()); $i++) {
+        for ($i = 0; $i < $nIn; $i++) {
             $inputs[] = new PSBTInput();
         }
+        $nOut = count($tx->getOutputs());
         $outputs = [];
-        for ($i = 0; $i < count($tx->getOutputs()); $i++) {
+        for ($i = 0; $i < $nOut; $i++) {
             $outputs[] = new PSBTOutput();
         }
-
         return new PSBT($tx, $unknowns, $inputs, $outputs);
     }
 }

src/Transaction/PSBT/PSBT.php

@@ -167,8 +167,9 @@ public function getTransaction(): TransactionInterface
     {
         return $this->tx;
     }
+
     /**
-     * @return string[]
+     * @return BufferInterface[]
      */
     public function getUnknowns(): array
     {

src/Transaction/PSBT/PSBTInput.php

@@ -373,6 +373,9 @@ public function getFinalizedScriptWitness(): ScriptWitnessInterface
         return $this->finalScriptWitness;
     }
 
+    /**
+     * @return BufferInterface[]
+     */
     public function getUnknownFields(): array
     {
         return $this->unknown;

src/Transaction/PSBT/PSBTOutput.php

@@ -161,7 +161,7 @@ public function getBip32Derivations(): array
     }
 
     /**
-     * @return string[]
+     * @return BufferInterface[]
      */
     public function getUnknownFields(): array
     {