if you have not customize domain's virtual hosting templates, you can perform following workaround:
mkdir -p /usr/local/psa/admin/conf/templates/custom/service
cp /usr/local/psa/admin/conf/templates/default/domain/domainVirtualHost.php /usr/local/psa/admin/conf/templates/custom/
than create files with following content:
cat /usr/local/psa/admin/conf/templates/custom/service/php.php
<IfModule <?php echo $VAR->server->webserver->apache->php4ModuleName ?>>
<Files ~ (\.php$)>
<?php
if ($OPT['enabled']) {
echo "php_admin_flag engine on\n";
if (isset($OPT['settings'])) {
echo $OPT['settings'];
}
} else {
echo "php_admin_flag engine off\n";
}
?>
</Files>
</IfModule>
<IfModule mod_php5.c>
<Files ~ (\.php$)>
<?php
if (array_key_exists('enabled', $OPT) && $OPT['enabled']) {
echo "php_admin_flag engine on\n";
if (isset($OPT['settings'])) {
echo $OPT['settings'];
}
} else {
echo "php_admin_flag engine off\n";
}
?>
</Files>
</IfModule>
cat /usr/local/psa/admin/conf/templates/custom/service/php_over_cgi.php
<Files ~ (\.php$)>
SetHandler None
AddHandler php-script .php
Options +ExecCGI
allow from all
</Files>
cat /usr/local/psa/admin/conf/templates/custom/service/php_over_fastcgi.php
<IfModule mod_fcgid.c>
<Files ~ (\.php$)>
SetHandler fcgid-script
FCGIWrapper <?php echo $VAR->server->webserver->apache->phpCgiBin ?> .php
Options +ExecCGI
allow from all
</Files>
</IfModule>