diff --git a/php/run-php-tests.sh b/php/run-php-tests.sh
index e5cfc0d96..80758bdaa 100755
--- a/php/run-php-tests.sh
+++ b/php/run-php-tests.sh
@@ -28,10 +28,13 @@ cd extension
 # won't get passed down to the script.  Furthermore, setting debug or
 # trace isn't very useful anyway because the PHP test script mixes
 # stdout and stderr together and compares this to the expected output,
-# so you'd just get failures for every test.  So there is no good way
-# to debug libguestfs failures in PHP tests, but if an individual test
-# fails locally then you can edit the guestfs_php_*.phpt.in and
-# uncomment the putenv statement, then look at the output.
+# so you'd just get failures for every test.
+#
+# So there is no good way to debug libguestfs failures in PHP tests,
+# but if an individual test fails and you want to find out more, you
+# can comment out the following two 'unset' statements.  The tests
+# will definitely fail if you do this, but you will be able to see the
+# debug output in the '*.out' files.
 
 unset LIBGUESTFS_DEBUG
 unset LIBGUESTFS_TRACE
@@ -44,4 +47,8 @@ printenv | grep -E '^(LIBGUESTFS|LIBVIRT|LIBVIRTD|VIRTLOCKD|LD|MALLOC)_' >> env
 TESTS=$(echo tests/guestfs_*.phpt)
 echo TESTS: $TESTS
 
-${MAKE:-make} test TESTS="$TESTS" PHP_EXECUTABLE="$PWD/php-for-tests.sh" REPORT_EXIT_STATUS=1 TEST_TIMEOUT=300
+${MAKE:-make} test \
+              TESTS="$TESTS" \
+              TEST_PHP_EXECUTABLE="$PWD/php-for-tests.sh" \
+              REPORT_EXIT_STATUS=1 \
+              TEST_TIMEOUT=300