to install the open source free apache server in your linux, you can send this command, i am using Debian so this command i use:

apt-get install apache2


then you will see the installar begin the installation:
Reading Package Lists... Done
Building Dependency Tree... Done
The following extra packages will be installed:
liapache2-mpm-worker apache2-utils apache2.2-common libapr1 libaprutil1 libexpat1 libgcrypt11 libgnutls13 libgpg-error0
libldap2 libmagic1 libopencdk8 libpq4 libsasl2-2 libsqlite3-0 libtasn1-3 mime-support
Suggested packages:
rng-tools gnutls-bin file
Recommended packages:
libsasl2-modules libtasn1-3-bin
The following NEW packages will be installed:
apache2 apache2-mpm-worker apache2-utils apache2.2-common libapr1 libaprutil1 libexpat1 libgnutls13 libldap2 libmagic1
libpq4 libsasl2-2 libsqlite3-0 libtasn1-3 mime-support
The following packages will be upgraded:
libgcrypt11 libgpg-error0 libopencdk8


Setting up apache2-mpm-worker (2.2.3-4) ...
Starting web server (apache2)....

Setting up apache2 (2.2.3-4) ...


NEXT STEP if you want to install PHP CLICK HERE