В терминале попробовал. Мой лог.
al@ubuntu-desktop1:~/Desktop/Programming/php$ cat ./del.php
#! /usr/bin/php5
<?php
echo "Hello, PHP!\n"
// gzip();
?>
al@ubuntu-desktop1:~/Desktop/Programming/php$ ./del.php
Hello, PHP!
al@ubuntu-desktop1:~/Desktop/Programming/php$ cat ./del.php
#! /usr/bin/php5
<?php
echo "Hello, PHP!\n"
gzip();
?>
al@ubuntu-desktop1:~/Desktop/Programming/php$ ./del.php
Parse error: syntax error, unexpected T_STRING, expecting ',' or ';' in /home/al/Desktop/Programming/php/del.php on line 4
al@ubuntu-desktop1:~/Desktop/Programming/php$
al@ubuntu-desktop1:~/Desktop/Programming/php$ cat ./del.php
#! /usr/bin/php5
<?php
echo "Hello, PHP!\n";
gzip();
?>
al@ubuntu-desktop1:~/Desktop/Programming/php$ ./del.php
Hello, PHP!
Fatal error: Call to undefined function gzip() in /home/al/Desktop/Programming/php/del.php on line 4
al@ubuntu-desktop1:~/Desktop/Programming/php$