Allow zero value fields support for NUMBER field type in WP Job Manager

functions.php

<?php

add_filter( 'submit_job_form_fields', 'smyles_allow_zero_value_field' );

function smyles_allow_zero_value_field( $fields ){
	$fields['job']['METAKEY']['before_sanitize'] = true;
	return $fields;
}

add_filter( 'job_manager_get_posted_number_field', 'smyles_allow_zero_value_number_field_handler' );

function smyles_allow_zero_value_number_field_handler(){
	return 'smyles_allow_zero_value_number_field';
}

function smyles_allow_zero_value_number_field( $key, $field ){

	if( isset( $_POST[ $key ] ) ){
		return sanitize_text_field( $_POST[ $key ] );
	}

	return '';
}

resumes.php

<?php

add_filter( 'submit_resume_form_fields', 'smyles_allow_resume_zero_value_field' );

function smyles_allow_resume_zero_value_field( $fields ){
	$fields['resume_fields']['METAKEY']['before_sanitize'] = true;
	return $fields;
}

add_filter( 'job_manager_get_posted_number_field', 'smyles_allow_zero_value_number_field_handler' );

function smyles_allow_zero_value_number_field_handler(){
	return 'smyles_allow_zero_value_number_field';
}

function smyles_allow_zero_value_number_field( $key, $field ){

	if( isset( $_POST[ $key ] ) ){
		return sanitize_text_field( $_POST[ $key ] );
	}

	return '';
}

New alternative approach for WP Job Manager 1.36.0+
https://gist.github.com/tripflex/a467508965eff64f13f94de55b7636b4