Sunday, June 12, 2016

nabphpinterview

to check the path to php.ini.
The PHP parsing engine needs a way to differentiate PHP code from other elements in the page. The mechanism for doing so is known as 'escaping to PHP.'
Whitespace is the stuff you type that is typically invisible on the screen, including spaces, tabs, and carriage returns end−of−linecharacters
. PHP whitespace insensitive means that it almost never matters how many whitespace characters you have in a row.one whitespace character is the same as many such characters.
Yes!
Here are the most important things to know about variables in PHP.
  • All variables in PHP are denoted with a leading dollar sign $
  • .
  • The value of a variable is the value of its most recent assignment.
  • Variables are assigned with the = operator, with the variable on the left-hand side and the expression to be evaluated on the right.
  • Variables can, but do not need, to be declared before assignment.
  • Variables in PHP do not have intrinsic types - a variable does not know in advance whether it will be used to store a number or a string of characters.
  • Variables used before they are assigned have default values.
  • PHP does a good job of automatically converting types from one to another when necessary.
  • PHP variables are Perl-like.
PHP has a total of eight data types which we use to construct our variables −
  • Integers − are whole numbers, without a decimal point, like 4195.
  • Doubles − are floating-point numbers, like 3.14159 or 49.1.
  • Booleans − have only two possible values either true or false.
  • NULL − is a special type that only has one value: NULL.
  • Strings − are sequences of characters, like 'PHP supports string operations.'
  • Arrays − are named and indexed collections of other values.
  • Objects − are instances of programmer-defined classes, which can package up both other kinds of values and functions that are specific to the class.
  • Resources − are special variables that hold references to resources external to PHP suchasdatabaseconnections
  • .
Rules for naming a variable are following −
  • Variable names must begin with a letter or underscore character.
  • A variable name can consist of numbers, letters, underscores but you cannot use characters like + , - , % , ,
  • . & , etc
Here are the rules for determine the "truth" of any value not already of the Boolean type −
  • If the value is a number, it is false if exactly equal to zero and true otherwise.
  • If the value is a string, it is false if the string is empty haszerocharacters
  • or is the string "0", and is true otherwise.
    • .
    • Don't use double as Booleans.

    NULL is a special type that only has one value: NULL. To give a variable the NULL value, simply assign it like this −
    $my_var = NULL;
    The special constant NULL is capitalized by convention, but actually it is case insensitive; you could just as well have typed −
    $my_var = null;
    A variable that has been assigned NULL has the following properties:
    It evaluates to FALSE in a Boolean context.
    It returns FALSE when tested with IsSet
    function.
    To define a constant you have to use define
    function and to retrieve the value of a constant, you have to simply specifying its name. Unlike with variables, you do not need to have a constant with a $.
    As indicated by the name, this function will return the value of the constant. This is useful when you
    want to retrieve value of a constant, but you do not know its name, i.e. It is stored in a variable or returned by a function.
    <?php
define("MINSIZE", 50);
echo MINSIZE;
echo constant("MINSIZE"); // same thing as the previous line
?>
    Only scalar data boolean,integer,floatandstring
    can be contained in constants.
    • There is no need to write a dollar sign $
    • function.
    • Constants may be defined and accessed anywhere without regard to variable scoping rules.
    • Once the Constants have been set, may not be redefined or undefined.

    PHP provides a large number of predefined constants to any script which it runs known as magic constants.
    _LINE_ − The current line number of the file.
    _FILE_ − The full path and filename of the file. If used inside an include,the name of the included file is returned. Since PHP 4.0.2, _FILE_ always contains an absolute path whereas in older versions it contained relative path under some circumstances.
    _FUNCTION_ − The function name. AddedinPHP4.3.0
    As of PHP 5 this constant returns the function name as it was declared case−sensitive
    . In PHP 4 its value is always lowercased.
    _CLASS_ − The class name. AddedinPHP4.3.0
    As of PHP 5 this constant returns the class name as it was declared case−sensitive
    . In PHP 4 its value is always lowercased.
    _METHOD_ − The class method name. AddedinPHP5.0.0
    The method name is returned as it was declared case−sensitive
    .
    break terminates the for loop or switch statement and transfers execution to the statement immediately following the for loop or switch.
    continue causes the loop to skip the remainder of its body and immediately retest its condition prior to reiterating.
    The foreach statement is used to loop through arrays. For each pass the value of the current array element is assigned to $value and the array pointer is moved by one and in the next pass next element will be processed.
    foreach (array as value)
{
    code to be executed;
}
    Numeric array − An array with a numeric index. Values are stored and accessed in linear fashion.
    Associative array − An array with strings as index. This stores element values in association with key values rather than in a strict linear index order.
    Multidimensional array − An array containing one or more arrays and values are accessed using multiple indices.
    To concatenate two string variables together, use the dot .
    operator −
    <?php
$string1="Hello World";
$string2="1234";
echo $string1 . " " . $string2;
?>
    This will produce following result −
    Hello World 1234
    The strlen
    function is used to find the length of a string. Let's find the length of our string "Hello world!" −
    <?php
echo strlen("Hello world!");
?>
    This will produce following result −
    12
    The strpos
    function is used to search for a string or character within a string. If a match is found in the string, this function will return the position of the first match. If no match is found, it will return FALSE. Let's see if we can find the string "world" in our string −
    <?php
echo strpos("Hello world!","world");
?>
    This will produce following result −
    6
    PHP provides a function getenv
    to access the value of all the environment variables.
    One of the environemnt variables set by PHP is HTTP_USER_AGENT which identifies the user's browser and operating system.
    The PHP rand
    function is used to generate a random number. This function can generate numbers with-in a given range. The random number generator should be seeded to prevent a regular pattern of numbers being generated. This is achieved using the srand
    function that specifiies the seed number as its argument.
    The PHP default variable $_PHP_SELF is used for the PHP script name and when you click "submit" button then same PHP script will be called.
    The PHP header
    function supplies raw HTTP headers to the browser and can be used to redirect it to another location. The redirection script should be at the very top of the page to prevent any other part of the page from loading. The target is specified by the Location: header as the argument to the header function. After calling this function the exit
    function can be used to halt parsing of rest of the code.
    The HTTP header will be different from the actual header where we send Content-Type as text/html\n\n. In this case content type will be application/octet-stream and actual file name will be concatenated alongwith it. For example,if you want make a FileName file downloadable from a given link then its syntax will be as follows.
    #!/usr/bin/perl
# HTTP Header
print "Content-Type:application/octet-stream; name=\"FileName\"\r\n";
print "Content-Disposition: attachment; filename=\"FileName\"\r\n\n";
# Actual File Content
open( FILE, "<FileName" );
while(read(FILE, $buffer, 100) )
{
   print("$buffer");
}
    The PHP provides $_GET associative array to access all the sent information using GET method.
    The PHP provides $_POST associative array to access all the sent information using POST method.
    The PHP REQUESTvariablecontainsthecontentsofboth
    _GET, POST,and_COOKIE. We will discuss COOKIEvariablewhenwewillexplainaboutcookies.ThePHP
    _REQUEST variable can be used to get the result from form data sent with both the GET and POST methods.
    array
    − Creates an array.
    sort
    − Sorts an array.
    Singly quoted strings are treated almost literally, whereas doubly quoted strings replace variables with their values as well as specially interpreting certain character sequences.
    <?php
$variable = "name";
$literally = 'My $variable will not print!\\n';
print($literally);
print "<br />";
$literally = "My $variable will print!\\n";
print($literally);
?>
    This will produce following result −
    My $variable will not print!\n
My name will print
    To concatenate two string variables together, use the dot .
    operator.
    <?php
$string1="Hello World";
$string2="1234";
echo $string1 . " " . $string2;
?>
    This will produce following result −
    Hello World 1234
    The PHP REQUESTvariablecontainsthecontentsofboth
    _GET, POST,and_COOKIE. We will discuss COOKIEvariablewhenwewillexplainaboutcookies.ThePHP
    _REQUEST variable can be used to get the result from form data sent with both the GET and POST methods.
    There are two PHP functions which can be used to included one PHP file into another PHP file.
    • The include
    • Function
    Function and require
    If there is any problem in loading a file then the require
    function generates a fatal error and halt the execution of the script whereas include
    function generates a warning but the script will continue execution.
    The PHP fopen
    function is used to open a file. It requires two arguments stating first the file name and then mode in which to operate. "r" mode opens the file for reading only and places the file pointer at the beginning of the file.
    Once a file is opened using fopen
    function it can be read with a function called fread
    . This function requires two arguments. These must be the file pointer and the length of the file expressed in bytes.
    The files's length can be found using the filesize
    function which takes the file name as its argument and returns the size of the file expressed in bytes.
    File's existence can be confirmed using file_exist
    function which takes file name as an argument.
    Yes! You can set a parameter to have a default value if the function's caller doesn't pass it.
    PHP provided setcookie
    function to set a cookie. This function requires upto six arguments and should be called before <html> tag. For each cookie this function has to be called separately.
    setcookie(name, value, expire, path, domain, security);
    PHP provides many ways to access cookies. Simplest way is to use either COOKIEor
    HTTP_COOKIE_VARS variables.
    You can use isset
    function to check if a cookie is set or not.
    To delete a cookie you should call setcookie
    with the name argument only.
    A PHP session is easily started by making a call to the session_start
    function.This function first checks if a session is already started and if none is started then it starts one. It is recommended to put the call to session_start
    at the beginning of the page.
    Session variables are stored in associative array called $_SESSION[]. These variables can be accessed during lifetime of a session.
    Make use of isset
    function to check if session variable is already set or not.
    Here is the example to unset a single variable −
    <?php
   unset($_SESSION['counter']);
?>
    A PHP session can be destroyed by session_destroy
    function.
    PHP makes use of mail
    function to send an email. This function requires three mandatory arguments that specify the recipient's email address, the subject of the the message and the actual message additionally there are other two optional parameters.
    mail( to, subject, message, headers, parameters );
    This is a global PHP variable. This variable is an associate double dimension array and keeps all the information related to uploaded file.
    Using $_FILES['file']['tmp_name'] − it provides access to the uploaded file in the temporary directory on the web server.
    Using $_FILES['file']['name'] − it provides the actual name of the uploaded file.
    Using $_FILES['file']['size'] − it provides the size in bytes of the uploaded file.
    Using $_FILES['file']['type'] − it provides the MIME type of the uploaded file.
    Using $_FILES['file']['error'] − it provides the error code associated with this file upload.
    $GLOBALS − Contains a reference to every variable which is currently available within the global scope of the script. The keys of this array are the names of the global variables.
    $_SERVER − This is an array containing information such as headers, paths, and script locations. The entries in this array are created by the web server. There is no guarantee that every web server will provide any of these. See next section for a complete list of all the SERVER variables.
    $_COOKIE − An associative array of variables passed to the current script via HTTP cookies.
    $_SESSION − An associative array containing session variables available to the current script.
    $_PHP_SELF − A string containing PHP script file name in which it is called.
    phperrormsg−
    php_errormsg is a variable containing the text of the last error message generated by PHP.
    ereg
    − The ereg
    function searches a string specified by string for a string specified by pattern, returning true if the pattern is found, and false otherwise.
    eregi
    − The eregi
    function searches throughout a string specified by pattern for a string specified by string. The search is not case sensitive.
    The split
    function will divide a string into various elements, the boundaries of each element based on the occurrence of pattern in string.
    preg_match
    - The preg_match
    function searches string for pattern, returning true if pattern exists, and false otherwise.
    The preg_split
    function operates exactly like split
    , except that regular expressions are accepted as input parameters for pattern.
    Using getMessage
    method of Exception class which returns the message of exception.
    Using getCode
    method of Exception class which returns the code of exception.
    Using getFile
    method of Exception class which returns source filename.
    Using getLine
    method of Exception class which returns source line.
    Using getTrace
    method of Exception class which returns array of the backtrace.
    Using getTraceAsString
    method of Exception class which returns formated string of trace.
    PHP's time
    function gives you all the information that you need about the current date and time. It requires no arguments but returns an integer.
    The function getdate
    optionally accepts a time stamp and returns an associative array containing information about the date. If you omit the time stamp, it works with the current time stamp as returned by time
    .
    The date
    function returns a formatted string representing a date. You can exercise an enormous amount of control over the format that date
    returns with a string argument that you must pass to it.
    PHP provides mysql_connect function to open a database connection.
    connection mysql_connect(server,user,passwd,new_link,client_flag);
    PHP uses mysql_query function to create a MySQL database. This function takes two parameters and returns TRUE on success or FALSE on failure.
    bool mysql_query( sql, connection );
    Its simplest function mysql_close PHP provides to close a database connection. This function takes connection resource returned by mysql_connect function. It returns TRUE on success or FALSE on failure.
    bool mysql_close ( resource $link_identifier );
    If a resource is not specified then last opend database is closed.
    PHP 5's new SimpleXML module makes parsing an XML document, well, simple. It turns an XML document into an object that provides structured access to the XML. To create a SimpleXML object from an XML document stored in a string, pass the string to simplexml_load_string
    . It returns a SimpleXML object.
    Yes!
    PHP provides a special function called __construct
    to define a constructor. You can pass as many as arguments you like into the constructor function.
    Like a constructor function you can define a destructor function using function __destruct
  • Values of type NULL are always false.
  • If the value is an array, it is false if it contains no other values, and it is true otherwise. For an object, containing a value means having a member variable that has been assigned a value.
  • Valid resources are true althoughsomefunctionsthatreturnresourceswhentheyaresuccessfulwillreturnFALSEwhenunsuccessful
  • before a constant, where as in Variable one has to write a dollar sign.
  • Constants cannot be defined by simple assignment, they may only be defined using the define
  • Function
  • The require
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