Php – Error while installing php extension ‘expect’

I got some serious error while installing expect extension in PHP.

I ran sudo pecl install channel://pecl.php.net/expect-0.3.1

I got error like this while running make,

running: make
/bin/bash /tmp/pear/temp/pear-build-rootvXp7LZ/expect-0.3.1/libtool --mode=compile cc  -I. -I/tmp/pear/temp/expect -DPHP_ATOM_INC -I/tmp/pear/temp/pear-build-rootvXp7LZ/expect-0.3.1/include -I/tmp/pear/temp/pear-build-rootvXp7LZ/expect-0.3.1/main -I/tmp/pear/temp/expect -I/usr/include/php5 -I/usr/include/php5/main -I/usr/include/php5/TSRM -I/usr/include/php5/Zend -I/usr/include/php5/ext -I/usr/include/php5/ext/date/lib  -DHAVE_CONFIG_H  -g -O2   -c /tmp/pear/temp/expect/expect.c -o expect.lo
libtool: compile:  cc -I. -I/tmp/pear/temp/expect -DPHP_ATOM_INC -I/tmp/pear/temp/pear-build-rootvXp7LZ/expect-0.3.1/include -I/tmp/pear/temp/pear-build-rootvXp7LZ/expect-0.3.1/main -I/tmp/pear/temp/expect -I/usr/include/php5 -I/usr/include/php5/main -I/usr/include/php5/TSRM -I/usr/include/php5/Zend -I/usr/include/php5/ext -I/usr/include/php5/ext/date/lib -DHAVE_CONFIG_H -g -O2 -c /tmp/pear/temp/expect/expect.c  -fPIC -DPIC -o .libs/expect.o
In file included from /tmp/pear/temp/expect/expect.c:21:0:
/tmp/pear/temp/expect/php_expect.h:33:17: fatal error: tcl.h: No such file or directory
compilation terminated.
make: *** [expect.lo] Error 1
ERROR: `make' failed

Please advice me as I am a very beginner in PHP.

Thanks.