Q. Difference in echo and print???
1.
Speed. There is a
difference between the two, but speed-wise it should be irrelevant which one
you use. echo is marginally faster since it doesn't set a return value if you
really want to get down to the nitty gritty.
2.
Expression. print() behaves
like a function in that you can do: $ret = print "Hello World";
And $ret will be 1. That means that print can be used as part of
a more complex expression where echo cannot. An example from the PHP Manual:
$b ? print "true" : print "false";
print is also part of the precedence table
which it needs to be if it is to be used within a complex expression. It is
just about at the bottom of the precedence list though. Only "," AND,
OR and XOR are lower.
3.
Parameter(s). The
grammar is: echo expression [, expression[, expression] ...
] But echo ( expression, expression ) is not valid. This would
be valid: echo ("howdy"),("partner"); the same
as: echo "howdy","partner"; (Putting the brackets in
that simple example serves no purpose since there is no operator precedence
issue with a single term like that.)
So, echo without parentheses can take multiple
parameters, which get concatenated:
echo "and a ", 1, 2, 3; // comma-separated
without parentheses
echo ("and a 123"); // just one parameter with parentheses
print() can only
take one parameter:
print ("and a 123");
print "and a 123";
Q. What are super global variable
and example
9 variables in PHP are
"superglobals", which means that they are always accessible,
regardless of scope - and you can access them from any function, class or file
without having to do anything special.
The PHP superglobal
variables are:
- $_GET
- $_POST
- $_REQUEST
- $_FILES
- $_COOKIE
- $_SESSION
- $GLOBALS
- $_SERVER
- $_ENV
$GLOBALS is a PHP super global variable which is used to access
global variables from anywhere in the PHP script (also from within functions or
methods).PHP stores all global variables in an array called $GLOBALS[index].
The index holds the name of the variable.
<?php
$x = 75;
$y = 25;
function addition() {
$GLOBALS['z'] = $GLOBALS['x']
+ $GLOBALS['y'];
}
addition();
echo $z;
?>
$_SERVER is
a PHP super global variable which holds information about headers, paths, and
script locations.
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$_SERVER['PHP_SELF']
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Returns the filename
of the currently executing script
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$_SERVER['GATEWAY_INTERFACE']
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Returns the version of
the Common Gateway Interface (CGI) the server
is using
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$_SERVER['SERVER_ADDR']
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Returns the IP address
of the host server
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$_SERVER['SERVER_NAME']
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Returns the name of
the host server (such as www.w3schools.com)
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$_SERVER['SERVER_SOFTWARE']
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Returns the server
identification string
(such as Apache/2.2.24)
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$_SERVER['SERVER_PROTOCOL']
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Returns the name and
revision of the information protocol
(such as HTTP/1.1)
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$_SERVER['REQUEST_METHOD']
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Returns the request
method used to access the page
(such as POST)
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$_SERVER['REQUEST_TIME']
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Returns the timestamp
of the start of the request
(such as 1377687496)
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$_SERVER['QUERY_STRING']
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Returns the query
string if the page is accessed via
a query string
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$_SERVER['HTTP_ACCEPT']
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Returns the Accept
header from the current request
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$_SERVER['HTTP_ACCEPT_CHARSET']
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Returns the
Accept_Charset header from the current request
(such as
utf-8,ISO-8859-1)
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$_SERVER['HTTP_HOST']
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Returns the Host
header from the current request
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$_SERVER['HTTP_REFERER']
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Returns the complete URL
of the current page (
not reliable because
not all user-agents support it)
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$_SERVER['HTTPS']
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Is the script queried
through a secure HTTP protocol
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$_SERVER['REMOTE_ADDR']
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Returns the IP address
from where the user is viewing the current page
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$_SERVER['REMOTE_HOST']
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Returns the Host name
from where the user is viewing the current page
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$_SERVER['REMOTE_PORT']
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Returns the port being
used on the user's machine to
communicate with the
web server
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$_SERVER['SCRIPT_FILENAME']
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Returns the absolute pathname
of the currently
executing script
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$_SERVER['SERVER_ADMIN']
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Returns the value
given to the SERVER_ADMIN
directive in the web server configuration
file
(if your script runs
on a virtual host, it will be
the value defined for
that virtual host)
(such as someone@w3schools.com)
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$_SERVER['SERVER_PORT']
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Returns the port on
the server machine being used by
the web server
for communication (such as 80)
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$_SERVER['SERVER_SIGNATURE']
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Returns the server
version and virtual host name which are added
to server-generated
pages
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$_SERVER['PATH_TRANSLATED']
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Returns the file
system based path to the current script
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$_SERVER['SCRIPT_NAME']
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Returns the path of
the current script
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$_SERVER['SCRIPT_URI']
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Returns the URI of the
current page
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$_GET: limit
2000 characters, send via url, data
can be seen, no security, files images can’t be sent, we can bookmark a page
$_POST:
all names/values are embedded within the body of the HTTP
request, has no limit, secure, files images can be sent, variable are not seen
show we can bookmark a page
$_FILES: enctype="multipart/form-data" must be
added to form, method will be post,
move_uploaded_file($_FILES['photo']['tmp_name'],"uploads/candidate/photo/".$photo)
Getimagesize() to get uploading image height and
width
file_exists(url) to check file exist or not
if
($_FILES["fileToUpload"]["size"] > 500000) limit upload
$imageFileType =
pathinfo($target_file,PATHINFO_EXTENSION); to get extension
$_COOKIE:
A cookie is often used to identify a user. A cookie is a
small file that the server embeds on the user's computer. Each time the same
computer requests a page with a browser, it will send the cookie too. With PHP,
you can both create and retrieve cookie values
setcookie(name, value, expire, path, domain,
secure, httponly);
$cookie_name = "user";
$cookie_value = "John Doe";
setcookie($cookie_name, $cookie_value, time() +
(86400 * 30), "/"); // 86400 = 1 day
To disable a cookie set cookie with past date.
if(count($_COOKIE) > 0) To check cookie is
enable
$_SESSION
A session is a way to store information (in variables) to be
used across multiple pages. It stores in tmp folder on the server.
session_start();
$_SESSION["favcolor"] =
"green";
session_destroy();session_unset(); unset($_SESSION["favcolor"]);
default time 24
minutes (1440 seconds)
increase sesion time // server should keep session data for AT LEAST 1 hour
ini_set('session.gc_maxlifetime', 3600);
// each client should remember their session id for EXACTLY 1 hour
session_set_cookie_params(3600);
session_start(); // ready to go!
To change session path: ini_set(session.save_path, '/path/to/your/folder')
ini_set('session.save_path',realpath(dirname($_SERVER['DOCUMENT_ROOT'])
. '/../session'));
session_start();
Apache used /var/tmp,
while CLI used something like /var/folders/kf/hk_dyn7s2z9bh7y_j59cmb3m0000gn/T
Get session
id $a = session_id();
if(empty($a)) session_start();
echo "SID: ".SID."<br>session_id(): ".session_id()."<br>COOKIE:
".$_COOKIE["PHPSESSID"];
Q. Headers in php: The header() function sends a raw HTTP
header to a client. It is important to notice that header() must be called
before any actual output is sent (In PHP 4 and later, you can use output buffering
to solve this problem)
header("Expires: Mon, 26 Jul 1997 05:00:00
GMT");
header("Cache-Control: no-cache");
header("Pragma: no-cache");
Let the user be prompted
to save a generated PDF file (Content-Disposition header is used to supply a
recommended filename and force the browser to display the save dialog box):
<?php
header("Content-type:application/pdf");
// It will be called downloaded.pdf
header("Content-Disposition:attachment;filename='downloaded.pdf'");
// The PDF source is in original.pdf
readfile("original.pdf");
?>
<html>
<body>
Q. How to concatate two strings
in php by . operater $a=”ram”.”test”;
String functions:
trim() along with ltrim() and rtrim() strip characters from
a string. trim($string) without any further arguments will strip all spaces,
carriage returns, new lines, null characters, and vertical tabs from $string.
trim($string, 'ld'): Hello
Wor
str_replace() replaces all instances of a given
character with another. To strip out all ‘l’s from our string, use
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echo str_replace('l',
'', $string);
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This returns “Heo Word”.
strtolower() transforms a string into all lower-case letters.
Strtoupper(),strtotime(time), ucfirst($str),
ucwords($str)
echo strlen($string);
substr($string, 3);: lo World, after 3rd all charcter
echo substr($string,
-1); d from last 1 character
strpos($string, 'l'); :2, position of a
character in a string
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Removes whitespace or other characters from the right end of a
string
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Returns a string with backslashes in front of the specified
characters
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Returns a string with backslashes in front of predefined
characters
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Outputs one or more strings
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Outputs one or more strings
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Outputs a formatted string
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str_getcsv() function parses a string for
fields in CSV format and returns an array containing the fields read.
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Repeats a string a specified number of times
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Replaces some characters in a string (case-sensitive)
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Count the number of words in a string
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Splits a string into an array
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Finds the first occurrence of a string inside another string
(alias of strstr())
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Compares two strings (case-sensitive)
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Strips HTML and PHP tags from a string
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Returns the length of a string
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String comparison of the first n characters (case-sensitive)
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Returns the position of the first occurrence of a string inside
another string (case-sensitive)
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Q. PHP array
1.
Indexed array 2. Associative
array 3. Multidimensional array
1. Indexed
array
$cars = array("Volvo", "BMW",
"Toyota");
echo "I like " . $cars[0] . ",
" . $cars[1] . " and " . $cars[2] . ".";
Getting the length of the array: <?php echo
count($cars); ?>
2.Associative
array
<?php
$age =
array("Peter"=>"35", "Ben"=>"37",
"Joe"=>"43");
echo "Peter is " . $age['Peter'] .
" years old.";
foreach($age as $x => $x_value) {
echo "Key=" . $x .
", Value=" . $x_value;
echo "<br>";
}
?>
3.Multidimesional
array
$cars = array
(
array("Volvo",22,18),
array("BMW",15,13),
array("Saab",5,2),
array("Land Rover",17,15)
);
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Returns the values from a single column in the input array
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Creates an array by using the elements from one "keys"
array and one "values" array
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Counts all the values of an array
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Fills an array with values
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Fills an array with values, specifying keys
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Checks if the specified key exists in the array
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Merges one or more arrays into one array
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Deletes the last element of an array
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Inserts one or more elements to the end of an array
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Returns one or more random keys from an array
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Returns an array in the reverse order
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Searches an array for a given value and returns the key
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Removes the first element from an array, and returns the value
of the removed element
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Returns the sum of the values in an array
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Removes duplicate values from an array
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Sorts an associative array in descending order, according to the
value
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Sorts an associative array in ascending order, according to the
value
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Returns the number of elements in an array
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Returns the current element in an array
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Sets the internal pointer of an array to its last element
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Sorts an associative array in descending order, according to the
key
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Sorts an associative array in ascending order, according to the
key
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Sorts an indexed array in descending order
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Sorts an indexed array in ascending order
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Q. array.push, array.pop, how to
insert an element in an array
Q. Difference in array merge and
combinbe
Q. how you will check a variable
is array or not, or string/number
- ctype_digit() -
Check for numeric character(s)
- is_bool() -
Finds out whether a variable is a boolean
- is_null() -
Finds whether a variable is NULL
- is_float() -
Finds whether the type of a variable is float
- is_int() -
Find whether the type of a variable is integer
- is_string() -
Find whether the type of a variable is string
- is_object() -
Finds whether a variable is an object
- is_array() -
Finds whether a variable is an array
is_numeric — Finds whether a
variable is a number or a numeric string
Q
abstract, class, method, variable, polymorphism, function overloading, function
overriding,
polymorphism allows you define one interface and
have multiple implementations
two types are in java
1 method overloading also compile time: method
difned several times by changing argument data type and number of argument
2 method overriding
also runtime : defined function in base class also defined in child class
Abstract method: function only declare not
defined in the class
Abstract class: Classes defined as
abstract may not be instantiated, and any class that contains at least one
abstract method must also be abstract.
Abstract classes are classes that contain one or more abstract
methods. An abstract method is a method that is declared, but contains no
implementation. Abstract classes may not be instantiated, and require
subclasses to provide implementations for the abstract methods.
interfaces are abstract classes with no method
declared.
Default visibility public and only do not
support multiple inheritance.
Can implements many interface but can extend
only one class
Q.
final class and final method difference
if methode is final, it can’t be override and
if a class is final it can’t be extended.
Q
cookies
setcookie(name, value, expire, path, domain, security);
Here is the detail of all the arguments:
·
Name
- This
sets the name of the cookie and is stored in an environment variable called HTTP_COOKIE_VARS.
This variable is used while accessing cookies.
·
Value
-This sets the value of
the named variable and is the content that you actually want to store.
·
Expiry
- This specify a future time in seconds
since 00:00:00 GMT on 1st Jan 1970. After this time cookie will become
inaccessible. If this parameter is not set then cookie will automatically
expire when the Web Browser is closed.
·
Path
-This specifies the
directories for which the cookie is valid. A single forward slash character
permits the cookie to be valid for all directories.
·
Domain
- This
can be used to specify the domain name in very large domains and must contain
at least two periods to be valid. All cookies are only valid for the host and
domain which created them.
·
Security
- This can be set to 1 to specify that the
cookie should only be sent by secure transmission using HTTPS otherwise set to
0 which mean cookie can be sent by regular HTTP.
Following example will create two cookies name and age these cookies will be expired after
one hour.
<?php
setcookie("name", "John Watkin", time()+3600, "/","", 0);
setcookie("age", "36", time()+3600, "/", "", 0);
?>
<html>
<head>
<title>Setting Cookies with PHP</title>
</head>
<body>
<?php echo "Set Cookies"?>
</body>
</html>
Officially, to delete a cookie you should
call setcookie() with the name argument only but this does not always work
well, however, and should not be relied on.
It is safest to set the cookie with a date
that has already expired:
setcookie( "name", "", time()- 60, "/","", 0);
Q. what is $_server, how to get
browser name
echo $_SERVER['HTTP_USER_AGENT'] .
"\n\n";
$browser = get_browser(null,true);
Current url- <?php echo $_SERVER['REQUEST_URI']; ?>
Request method (get, post,put,delete) $_SERVER['REQUEST_METHOD']
Q. difference in fetch_associate
and fetch_array
fetch_array() returns two arrays, one with numeric
keys and other with associative strings (column names), so here you can either use $row['column_name'] or $row[0]
Where as fetch_assoc() will return string indexed key array
and no numeric array so you won't have an option here of using numeric keys
like $row[0]
So the latter one is better in
performance compared to fetch_array() and obviously using named indexes is
far better compared to numeric indexes.
Q. Difference between two dates
<?php
$datetime1
= new DateTime('2015-08-29');
$datetime2
= new DateTime('2015-08-30');
$interval
= $datetime1->diff($datetime2);
echo
$interval->format('%R%a days');
?>
relation
in session and cokkies
sesion
and cokkies details in depth
difference
between echo and print, which one is faster, is print return anything
what is
ksort in php
how you
will check a variable is array or not, or string/number echo gettype($value), "\n";
types of
array, how to declare them
plymorphism,
function overloading, overriding and inheritance in php
session
cokkie and how to use them and difference
what is
$_server, how to get browser name
echo $_SERVER['HTTP_USER_AGENT'] . "\n\n"; $browser = get_browser
(null,true);
checking
number result obtained mysqli_num_rows($result);
difference
in fetch_associate and fetch_array
constructer
and distructor
array
functions
finding
unique value in array
number
of days finding
swap two
number without uing third variable
class
and objects
what is
consutructer
inheritance
interface and abstract
method
overloading vs method overriding
array_merge
vs array_combine
strstr
vs strops
print
table without using loop
magic
methods and magic constants
if vs
switch
loop
levels
mysql_fetch_aray
and mysql_fetch_object
