PHP Developer’s Dictionary IT-SC book 190 int is_string(mixed var) Description The is_string() function returns true if var is a string and returns false otherwise. isset() Syntax int isset(mixed var) Description The isset() function returns true if var exists and returns false otherwise. $avar = 100; echo isset($avar);//displays 1 print_r() Syntax void print_r(mixed expression); Description The print_r() function, which was added in PHP 4.0, displays human-readable information about the values of variables. If expression is a string, integer, or double, the value itself will be printed. If expression is an array, the keys and values will be displayed. Similar notation is used for objects. $array1 = array (1,2,3); print_r($array1); //displays Array ( [0] => 1 [1] => 2 [2] => 3 ) settype() PHP Developer’s Dictionary IT-SC book 191 Syntax int settype(string var, string type) Description The settype() function sets the type of var to that of type . Possible values of type are "integer" , "double" , "string" , "array" , and "object" . The return value is true if the type could be set, and false otherwise. strval() Syntax string strval(mixed var) Description The strval() function returns the string representation of var . var must be a scalar type and not an array or object. unset() Syntax int unset(mixed var) Description The unset() function destroys the specified variable and returns true. var_dump() Syntax void var_dump(mixed expression ) Description PHP Developer’s Dictionary IT-SC book 192 The var_dump() function, which was added in PHP 3.0.5 and PHP 4.0, displays structured information about an expression, including its type and value. Arrays are processed recursively with values indented to show structure. $array1 = array (1,2,3); var_dump($array1); //displays array(3) { [0]=> int(1) [1]=> int(2) [2]=> int(3) } PHP Developer’s Dictionary IT-SC book 193 Chapter 6. Protocol Extensions On the Internet, there are lots of methods, called protocols , of moving files and data around from place to place. These protocols are what enable us to move files, send and receive email, download Web pages, manage networks, and much more. Within the PHP programming language are several sets of functions that provide the ability to use these protocols. They are the focus of this chapter and are as follows: • FTP • HTTP • IMAP, POP3, and NNTP • LDAP • SNMP FTP The File Transfer Protocol (FTP) is a standard Internet protocol that is used to exchange files. Generally speaking, FTP commands are issued either on a command- line interface or through an application. You can read the Request For Comments (RFC) on FTP at http://www.ietf.org/rfc/rfc0959.txt . Note For those of you using PHP 3, this library of functions was not added until 3.0.13. ftp_cdup() Syntax int ftp_cdup(int ftp_stream) Description The ftp_cdup() function instructs the connection to change to the parent directory of the current working directory in ftp_stream , which is the name handle of a previously opened stream using ftp_connect() . If successful, 1 is returned. If the function fails, 0 is returned. PHP Developer’s Dictionary IT-SC book 194 The following short example moves up one directory on the system, whose connection is defined by $my_conn. The result of the operation is stored in $status. If successful, this will contain 1 ; otherwise, it will contain an error message. $status = ftp_cdup($my_conn); ftp_chdir() Syntax int ftp_chdir(int ftp_stream, string directory) Description The ftp_chdir() function changes the current working directory of ftp_stream , which is the name handle of a previously opened stream using ftp_connect() , to directory . If successful, 1 is returned; otherwise 0 is returned on an error. ftp_connect() Syntax int ftp_connect(string host, int [port] ) Description The ftp_connect() function opens an FTP connection to host when successful. If the optional port is specified, the function attempts to open a connection to that specific port rather than to the default port 21. If the function fails, an error is returned. The following short example shows how you would connect to ftp.mcp.com and store the FTP stream reference in $my_conn . The result of the operation is stored in $status . If successful, this will contain 1 ; otherwise, it will contain an error message. $status = ftp_connect('ftp.mcp.com'); ftp_delete() Syntax . var_dump(mixed expression ) Description PHP Developer’s Dictionary IT-SC book 192 The var_dump() function, which was added in PHP 3.0.5 and PHP 4.0, displays structured information about. void print_r(mixed expression); Description The print_r() function, which was added in PHP 4.0, displays human-readable information about the values of variables. If expression is. (1,2,3); print_r($array1); //displays Array ( [0] => 1 [1] => 2 [2] => 3 ) settype() PHP Developer’s Dictionary IT-SC book 191 Syntax int settype(string var, string type) Description