无法在PHP和phing中访问jenkins的BUILD_NUMBER环境变量

Via entry point file

I invoke a php script from jenkins, using the "Execute shell" section -

php entry.php branch_name_${branch_name} deployment_group_${deployment_group} rollback_${rollback} last_successful_revision_${last_successful_revision} sanity_check_duration_start_time_delay_sec_${sanity_check_duration_start_time_delay_sec} sanity_check_duration_end_time_delay_sec_${sanity_check_duration_end_time_delay_sec}

I tried accessing the jenkins build number there, but it was not available -

$build_number = exec(${BUILD_NUMBER});
file_put_contents('/home/jenkins/deployment_beta/phing/new_test_sandeepan.txt', "
 Build number is ".$build_number, FILE_APPEND);

Log lin in that file shows -

 Build number is

Via phing xml file

I also tried accessing it in a phing xml file -

<appspecFileModifications buildName="${BUILD_NUMBER}" />

This xml file is invoked via the above mentioned entry file (php script), like this -

$last_output = exec("phing -q -Dbranch_name=".$branchName, $output);

I checked other questions like - How to use jenkins to declare BUILD_NUMBER environment variable in gradle? Jenkins - How to access BUILD_NUMBER environment variable