Olá,

1 – O erro:

# /etc/init.d/apache2 start
 * Starting web server apache2
 * The apache2 configtest failed.
Output of config test was:
/usr/sbin/apache2ctl: line 138: 23872 Segmentation fault      $HTTPD ${APACHE_ARGUMENTS} -t
Action 'configtest' failed.
The Apache error log may have more information.

2 – Cheque os modulos de php instalados:

ls -1 /etc/apache2/mods-enabled/*php*

3 – Desabilite o que não irá utilizar, exemplo:

a2dismod php5

4 – Reiniciar o apache:

service apache2 restart