diff --git a/day_5/functions.php b/day_5/functions.php
new file mode 100644
index 0000000..7fcaf8b
--- /dev/null
+++ b/day_5/functions.php
@@ -0,0 +1,78 @@
+<?php
+
+
+const MODE_POSITION = 0;
+const MODE_IMMEDIATE = 1;
+
+$input = explode(',', file_get_contents('input.txt'));
+
+function debug($message)
+{
+    echo $message."\n";
+}
+
+function run_opcode(array $input, $first_input = 1)
+{
+    $i = 0;
+    $output = 0;
+    do {
+        [$instruction, $first, $second, $position] = array_slice($input, $i, 4);
+        $instruction = str_pad($instruction, 5, '0', STR_PAD_LEFT);
+        $operation = (int) substr($instruction, -2);
+        $modes = array_map('intval', str_split(strrev(substr($instruction, 0, 3))));
+        $first = (int) ($modes[0] === MODE_IMMEDIATE ? $first : $input[$first]);
+        $second = (int) ($modes[1] === MODE_IMMEDIATE ? $second : $input[$second]);
+        switch ($operation) {
+            case 1:
+                $input[$position] = $first + $second;
+                debug(sprintf('Operation 1 : putting %s + %s = %s in position %s', $first, $second, ($first + $second), $position));
+                $i += 4;
+                break;
+            case 2:
+                $input[$position] = $first * $second;
+                debug(sprintf('Operation 1 : putting %s * %s = %s in position %s', $first, $second, ($first * $second), $position));
+                $i += 4;
+                break;
+            case 3:
+                $input[$input[$i+1]] = $first_input;
+                debug(sprintf('Operation 3 : putting %s in position %s', $first_input, $input[$i + 1]));
+                $i += 2;
+                break;
+            case 4:
+                $output = $input[$input[$i+1]];
+                debug(sprintf('Operation 4 : Outputting %s', $output));
+                $i += 2;
+                break;
+            case 5:
+                if ($first != 0) {
+                    $i = $second;
+                } else {
+                    $i += 3;
+                }
+                break;
+            case 6:
+                if ($first == 0) {
+                    $i = $second;
+                } else {
+                    $i += 3;
+                }
+                break;
+            case 7:
+                $input[$position] = $first < $second ? 1 : 0;
+                $i += 4;
+                break;
+            case 8:
+                $input[$position] = $first == $second ? 1 : 0;
+                $i += 4;
+                break;
+            case 99:
+                return $output;
+                exit;
+            default:
+                echo 'unknown operation : ' . $operation . '('.$i.')';
+                exit;
+        }
+    } while ($input[$i] !== 99);
+
+    return $output;
+}
\ No newline at end of file
diff --git a/day_5/part_1.php b/day_5/part_1.php
new file mode 100644
index 0000000..29ba4a7
--- /dev/null
+++ b/day_5/part_1.php
@@ -0,0 +1,5 @@
+<?php
+
+include 'functions.php';
+
+echo run_opcode($input);
\ No newline at end of file
diff --git a/day_5/part_2.php b/day_5/part_2.php
new file mode 100644
index 0000000..4504313
--- /dev/null
+++ b/day_5/part_2.php
@@ -0,0 +1,5 @@
+<?php
+
+include 'functions.php';
+
+echo run_opcode($input, 5);
\ No newline at end of file