Improve const phpdoc

Signed-off-by: Jack Cherng <jfcherng@gmail.com>

Author: jfcherng

src/SequenceMatcher.php

@@ -13,11 +13,20 @@
  */
 final class SequenceMatcher
 {
-    const OP_NOP = 0; // no operation
-    const OP_EQ = 1 << 0; // equal
-    const OP_DEL = 1 << 1; // delete
-    const OP_INS = 1 << 2; // insert
-    const OP_REP = 1 << 3; // replace
+    /** @var int 0, opcode: no operation */
+    const OP_NOP = 0;
+
+    /** @var int 1, opcode: equal */
+    const OP_EQ = 1 << 0;
+
+    /** @var int 2, opcode: delete */
+    const OP_DEL = 1 << 1;
+
+    /** @var int 4, opcode: insert */
+    const OP_INS = 1 << 2;
+
+    /** @var int 8, opcode: replace */
+    const OP_REP = 1 << 3;
 
     const OP_INT_TO_STR_MAP = [
         self::OP_NOP => 'nop',