Category: php

PHP – Maths Functions ”; Previous Next To enable mathematical operations, PHP has mathematical (arithmetic) operators and a number of mathematical functions. In this chapter, the following mathematical functions are explained with examples. PHP abs() Function The abs() function is an in-built function in PHP iterpreter. This function accepts any number as argument and returns a positive value, disregarding its sign. Absolute value of any number is always positive. abs( mixed $num) PHP abs() function returns the absolute value of num. If the data type of num is float, its return type will also be float. For integer parameter, the return type is integer. Example Take a look at this following example − <?php $num=-9.99; echo “negative float number: ” . $num . “n”; echo “absolute value : ” . abs($num) . “n”; $num=25.55; echo “positive float number: ” . $num . “n”; echo “absolute value : ” . abs($num). “n”; $num=-45; echo “negative integer number: ” . $num . “n”; echo “absolute value : ” . abs($num) . “n”; $num=25; echo “positive integer number: ” . $num . “n”; echo “absolute value : ” . abs($num); ?> It will produce the following output − negative float number: -9.99 absolute value : 9.99 positive float number: 25.55 absolute value : 25.55 negative integer number: -45 absolute value : 45 positive integer number: 25 absolute value : 25 PHP ceil() Function The ceil() function is an in-built function in PHP iterpreter. This function accepts any float number as argument and rounds it up to the next highest integer. This function always returns a float number as the range of float is bigger than that of integer. ceil ( float $num ) : float PHP ceil() function returns the smallest integer value that is bigger than or equal to given parameter. Example 1 The following code rounds 5.78 to its next highest integer which is 6 <?php $arg=5.78; $val=ceil($arg); echo “ceil(” . $arg . “) = ” . $val; ?> It will produce the following output − ceil(5.78) = 6 Example 2 The following example shows how you can find the next highest integer of 15.05. <?php $arg=15.05; $val=ceil($arg); echo “ceil(” . $arg . “) = ” . $val; ?> It will produce the following output − ceil(15.05) = 16 Example 3 For negative number, it is rounded towards 0. <?php $arg=-3.95; $val=ceil($arg); echo “ceil(” . $arg . “) = ” . $val; ?> It will produce the following output − ceil(-3.95) = -3 PHP exp() Function The exp() function calculates exponent of e that is Euler Number. PHP has a predefined constant M_E that represents Euler Number and is equal to 2.7182818284590452354. Hence, exp(x) returns 2.7182818284590452354x This function always returns a float. exp ( float $arg ) : float PHP exp() function returns the Euler Number e raised to given arg. Note that e is the base of natural algorithm. The exp() function is the inverse of natural logarithm. Example 1 One of the predefined constants in PHP is M_LN2 which stands for loge2 and is equal to 0.69314718055994530942. So, the exp() of this value will return 2. <?php echo “exp(” . M_LN2 . “) = ” . exp(M_LN2); ?> It will produce the following output − exp(0.69314718055995) = 2 Example 2 M_LN10 is another predefined constant representing loge10. This program calculates exp(M_LN10) and returns 10. <?php echo “exp(” . M_LN10 . “) = ” . exp(M_LN10); ?> It will produce the following output − exp(2.302585092994) = 10 PHP floor() Function The floor() function is another in-built function in PHP interpreter. This function accepts any float number as argument and rounds it down to the next lowest integer. This function always returns a float number as the range of float is bigger than that of integer. floor ( float $num ) : float PHP floor() function returns the largest integer less than or equal to the given parameter. Example 1 The following example shows how to round 15.05 to its next highest integer which is 15 <?php $arg=15.05; $val=floor($arg); echo “floor(” . $arg . “) = ” . $val; ?> It will produce the following output − floor(15.05) = 15 Example 2 The following example shows how to find the next lowest integer of 5.78. <?php $arg=5.78; $val=floor($arg); echo “floor(” . $arg . “) = ” . $val; ?> It will produce the following output − floor(5.78) = 5 Example 3 Negative numbers are rounded away from 0. <?php $arg=-3.95; $val=floor($arg); echo “floor(” . $arg . “) = ” . $val; ?> It will produce the following output − floor(-3.95) = -4 PHP intdiv() Function The intdiv() function returns the integer quotient of two integer parameters. If x/y results in “i” as division and “r” as remainder, then − x = y*i+r In this case, intdiv(x,y) returns “i” intdiv ( int $x , int $y ) : int The “x” parameter forms numerator part of the division expression, while the “y” parameter forms the denominator part of the division expression. PHP intdiv() function returns the integer quotient of division of “x” by “y”. The return value is positive if both the parameters are positive or both the parameters are negative. Example 1 The following example shows that if the numerator is less than the denominator, then intdiv() function returns 0. <?php $x=10; $y=3; $r=intdiv($x, $y);

PHP – Compound Types ”; Previous Next Data types in PHP can be of “scalar type” or “compound type”. Integer, float, Boolean and string types are scalar types, whereas array and object types are classified as compound types. Values of more than one types can be stored together in a single variable of a compound type. In PHP, objects and arrays are the two compound data types. An array is an ordered collection of elements of other data types, not necessarily of the same type. An object is an instance of either a built-in or a user defined class, consisting of properties and methods. Arrays in PHP An array is a data structure that stores one or more data values in a single variable. An array in PHP is an ordered map that associates the values to their keys. There are two ways to declare an array in PHP. One is to use the built-in array() function, and the other is to put the array elements inside square brackets. An array which is a collection of only values is called an indexed array. Each value is identified by a positional index staring from 0. If the array is a collection of key-value pairs, it is called as an associative array. The key component of the pair can be a number or a string, whereas the value part can be of any type. The array() Function in PHP The built-in array() function uses the parameters given to it and returns an object of array type. One or more comma-separated parameters are the elements in the array. array(mixed …$values): array Each value in the parenthesis may be either a singular value (it may be a number, string, any object or even another array), or a key-value pair. The association between the key and its value is denoted by the “=>” symbol. Example Take a look at this following example − $arr1 = array(10, “asd”, 1.55, true); $arr2 = array(“one”=>1, “two”=>2, “three”=>3); $arr3 = array( array(10, 20, 30), array(“Ten”, “Twenty”, “Thirty”), array(“physics”=>70, “chemistry”=>80, “maths”=>90) ); Using Square Brackets [ ] Instead of the array() function, the comma-separated array elements may also be put inside the square brackets to declare an array object. In this case too, the elements may be singular values or a string or another array. $arr1 = [10, “asd”, 1.55, true]; $arr2 = [“one”=>1, “two”=>2, “three”=>3]; $arr3 = [ [10, 20, 30], [“Ten”, “Twenty”, “Thirty”], [“physics”=>70, “chemistry”=>80, “maths”=>90] ]; Accessing Array Elements To access any element from a given array, you can use the array[key] syntax. For an indexed array, put the index inside the square bracket, as the index itself is anyway the key. <?php $arr1 = [10, 20, 30]; $arr2 = array(“one”=>1, “two”=>2, “three”=>3); var_dump($arr1[1]); var_dump($arr2[“two”]); ?> It will produce the following output − int(20) int(2) Array Traversal in PHP You can also use the foreach loop to iterate through an indexed array. <?php $arr1 = [10, 20, 30, 40, 50]; foreach ($arr1 as $val){ echo “$valn”; } ?> It will produce the following output − 10 20 30 40 50 Note that PHP internally treats the indexed array as an associative array, with the index being treated as the key. This fact can be verified by the var_dump() output of the array. We can unpack each element of the indexed array in the key and value variables with the foreach syntax − <?php $arr1 = [10, 20, 30, 40, 50]; foreach ($arr1 as $key => $val){ echo “arr1[$key] = $val” . “n”; } ?> It will produce the following output − arr1[0] = 10 arr1[1] = 20 arr1[2] = 30 arr1[3] = 40 arr1[4] = 50 The foreach loop is also used for iterating through an associative array, although any other type of loop can also be used with some maneuver. Let us look at the foreach loop implementation, with each k-v pair unpacked in two variables. <?php $capitals = array( “Maharashtra”=>”Mumbai”, “Telangana”=>”Hyderabad”, “UP”=>”Lucknow”, “Tamilnadu”=>”Chennai” ); foreach ($capitals as $k=>$v) { echo “Capital of $k is $v” . “n”; } ?> It will produce the following output − Capital of Maharashtra is Mumbai Capital of Telangana is Hyderabad Capital of UP is Lucknow Capital of Tamilnadu is Chennai Objects in PHP In PHP, an object is a compound data type. It is an instance of either a built in or user defined class. Given below is a simple PHP class − class SayHello { function hello() { echo “Hello World”; } } To declare an object of a class, we need to use the new operator. $obj=new SayHello; We can now call its method − <?php class SayHello { function hello() { echo “Hello World”. PHP_EOL; } } $obj=new SayHello; var_dump(gettype($obj)); $obj->hello(); ?> It will produce the following output − string(6) “object” Hello World stdClass PHP provides stdClass as a generic empty class which is useful for adding properties dynamically and casting. An object of stdClass is null to begin with. We can add properties to it dynamically. <?php $obj=new stdClass; $obj->name=”Deepak”; $obj->age=21; $obj->marks=75; print_r($obj); ?> It will produce the following output − stdClass Object ( [name] => Deepak [age] => 21 [marks] => 75 ) Array to Object Conversion in PHP An array in PHP can be typecast to an object as follows − <?php $arr=array(“name”=>”Deepak”, “age”=>21, “marks”=>75); $obj=(object)$arr; print_r($obj); ?> It will produce the following output − stdClass Object ( [name] => Deepak [age] =>

PHP – Files & I/O ”; Previous Next This chapter will explain following functions related to files − Opening a File Reading a File Writing a File Closing a File Opening and Closing Files 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. Files modes can be specified as one of the six options in this table. Sr.No Mode & Purpose 1 r Opens the file for reading only. Places the file pointer at the beginning of the file. 2 r+ Opens the file for reading and writing. Places the file pointer at the beginning of the file. 3 w Opens the file for writing only. Places the file pointer at the beginning of the file. and truncates the file to zero length. If files does not exist then it attempts to create a file. 4 w+ Opens the file for reading and writing only. Places the file pointer at the beginning of the file. and truncates the file to zero length. If files does not exist then it attempts to create a file. 5 a Opens the file for writing only. Places the file pointer at the end of the file. If files does not exist then it attempts to create a file. 6 a+ Opens the file for reading and writing only. Places the file pointer at the end of the file. If files does not exist then it attempts to create a file. If an attempt to open a file fails then fopen returns a value of false otherwise it returns a file pointer which is used for further reading or writing to that file. After making a changes to the opened file it is important to close it with the fclose() function. The fclose() function requires a file pointer as its argument and then returns true when the closure succeeds or false if it fails. Reading a 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 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. So here are the steps required to read a file with PHP. Open a file using fopen() function. Get the file”s length using filesize() function. Read the file”s content using fread() function. Close the file with fclose() function. Example The following example assigns the content of a text file to a variable then displays those contents on the web page. <html> <head> <title>Reading a file using PHP</title> </head> <body> <?php $filename = “tmp.txt”; $file = fopen( $filename, “r” ); if( $file == false ) { echo ( “Error in opening file” ); exit(); } $filesize = filesize( $filename ); $filetext = fread( $file, $filesize ); fclose( $file ); echo ( “File size : $filesize bytes” ); echo ( “<pre>$filetext</pre>” ); ?> </body> </html> It will produce the following result − Writing a File A new file can be written or text can be appended to an existing file using the PHP fwrite() function. This function requires two arguments specifying a file pointer and the string of data that is to be written. Optionally a third integer argument can be included to specify the length of the data to write. If the third argument is included, writing would will stop after the specified length has been reached. Example The following example creates a new text file then writes a short text heading inside it. After closing this file its existence is confirmed using file_exist() function which takes file name as an argument <?php $filename = “/home/user/guest/newfile.txt”; $file = fopen( $filename, “w” ); if( $file == false ) { echo ( “Error in opening new file” ); exit(); } fwrite( $file, “This is a simple testn” ); fclose( $file ); ?> <html> <head> <title>Writing a file using PHP</title> </head> <body> <?php $filename = “newfile.txt”; $file = fopen( $filename, “r” ); if( $file == false ) { echo ( “Error in opening file” ); exit(); } $filesize = filesize( $filename ); $filetext = fread( $file, $filesize ); fclose( $file ); echo ( “File size : $filesize bytes” ); echo ( “$filetext” ); echo(“file name: $filename”); ?> </body> </html> It will produce the following result − We have covered all the function related to file input and out in PHP File System Function chapter. Print Page Previous Next Advertisements ”;

PHP – Strings ”; Previous Next A string is a sequence of characters, like ”PHP supports string operations.” A string in PHP as an array of bytes and an integer indicating the length of the buffer. In PHP, a character is the same as a byte. This means that PHP only supports a 256-character set, and hence does not offer native Unicode support. PHP supports single quoted as well as double quoted string formation. Both the representations ”this is a simple string” as well as “this is a simple string” are valid. PHP also has Heredoc and Newdoc representations of string data type. Single-Quoted String A sequence of characters enclosed in single quotes (the character ”) is a string. $str = ”this is a simple string”; Example If you want to include a literal single quote, escape it with a backslash (). <?php $str = ”This is a ”simple” string”; echo $str; ?> It will give you the following output − This is a ”simple” string Example To specify a literal backslash, double it (\). <?php $str = ”The command C:\*.* will delete all files.”; echo $str; ?> Here is its output − The command C:*.* will delete all files. Example The escape sequences such as “r” or “n” will be treated literally and their special meaning will not be interpreted. The variables too will not be expanded if they appear in a single quoted string. <?php $str = ”This will not expand: n a newline”; echo $str . PHP_EOL; $x=100; $str = ”Value of x = $x”; echo $str; ?> It will produce the following output − This will not expand: n a newline Value of x = $x Double-Quoted String A sequence of characters enclosed in double-quotes (” “) is another string representation. $str = “this is a simple string”; Single-quoted and double-quoted strings are equivalent except for their treatment of escape sequences. PHP will interpret certain escape sequences for special characters. For example, “r” and “n”. Sequence Meaning n linefeed (LF or 0x0A (10) in ASCII) r carriage return (CR or 0x0D (13) in ASCII) t horizontal tab (HT or 0x09 (9) in ASCII) v vertical tab (VT or 0x0B (11) in ASCII) e escape (ESC or 0x1B (27) in ASCII) f form feed (FF or 0x0C (12) in ASCII) \ backslash $ dollar sign “ double-quote How to Escape Octal and Hexademical Characters in PHP? PHP supports escaping an Octal and a hexadecimal number to its ASCII character. For example, the ASCII character for P is 80 in decimal. 80 in decimal to Octal is 120. Similarly, 80 in decimal to hexadecimal is 50. To escape an octal character, prefix it with “”; and to escape a hexadecimal character, prefix it with “x”. <?php $str = “120110120”; echo “PHP with Octal: “. $str; echo PHP_EOL; $str = “x50x48x50”; echo “PHP with Hexadecimal: “. $str; ?> Check the output − PHP with Octal: PHP PHP with Hexadecimal: PHP As in single quoted strings, escaping any other character will result in the backslash being printed too. The most important feature of double-quoted strings is the fact that variable names will be expanded. Example A double-quoted string in PHP expands the variable names (PHP variables are prefixed with $ symbol). To actually represent a “$” symbol in a PHP string, escape it by prefixing with the “” character. <?php $price = 200; echo “Price = $ $price”; ?> You will get the following output − Price = $ 200 String Concatenation Operator To concatenate two string variables together, PHP uses the dot (.) operator − <?php $string1=”Hello World”; $string2=”1234″; echo $string1 . ” ” . $string2; ?> Here, you will get the following output − Hello World 1234 In the above example, we used the concatenation operator twice. This is because we had to insert a third string. Between the two string variables, we added a string with a single character, an empty space, to separate the two variables. The standard library of PHP includes many functions for string processing. They can be found at PHP’s official documentation (https://www.php.net/manual/en/ref.strings.php). The strlen() Function The strlen() function is used to find the length of a string. Example Let”s find the length of our string “Hello world!” − <?php echo strlen(“Hello world!”); ?> It will produce the following output − 12 The length of a string is often used in loops or other functions, when it is important to know when the string ends (that is, in a loop, we would want to stop the loop after the last character in the string). The strpos() Function 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. Example Let”s see if we can find the string “world” in our string − <?php echo strpos(“Hello world!”,”world”); ?> It will produce the following output − 6 As you can see, the position of the string “world” in our string is “6”. The reason that it is “6”, and not “7”, is that the first position in the string is

PHP – Installation ”; Previous Next You can start learning the basics of programming in PHP with the help of any of the online PHP compilers freely available on the Internet. This will help in getting acquainted with the features of PHP without installing it on your computer. Later on, install a full-fledged PHP environment on your local machine. One such online PHP compiler is provided by Tutorialpoint’s “Coding Ground for Developers”. Visit https://www.tutorialspoint.com/codingground.htm, enter PHP script and execute it. However, to be able to learn the advanced features of PHP, particularly related to the web concepts such as server variables, using backend databases, etc., you need to install the PHP environment on your local machine. In order to develop and run PHP Web pages, you neeed to install three vital components on your computer system. Web Server − PHP will work with virtually all Web Server software, including Microsoft”s Internet Information Server (IIS), NGNIX, or Lighttpd etc. The most often used web server software is the freely available Apache Server. Download Apache for free here − https://httpd.apache.org/download.cgi Database − PHP will work with virtually all database software, including Oracle and Sybase but most commonly used is freely available MySQL database. Download MySQL for free here − https://www.mysql.com/downloads/ PHP Parser − In order to process PHP script instructions a parser must be installed to generate HTML output that can be sent to the Web Browser. Although it is possible to install these three components separately, and configure the installation correctly, it is a little complex process, particularly for the beginners. Instead, using any all-in-one packaged distribution that contains precompiled Apache, MySQL and PHP binaries is convenient. XAMPP Installation There are many precompiled bundles available both in open-source as well as proprietary distributions. XAMPP, from Apache Friends (https://www.apachefriends.org/) is one of the most popular PHP enabled web server packages. We shall be using XAMPP in this tutorial. XAMPP is an easy to install Apache distribution that contains Apache, MariaDB, PHP and Perl. The letter X in the acronym indicates that it is a cross-platform software, available for use on Windows, Linux and OS X. Note that XAMPP includes MariaDB, which is a fork of MySQL, with no difference in its functionality. To download the respective installer for your operating system, visit https://www.apachefriends.org/download.html, and download one of the following − Windows − https://sourceforge.net/projects/ Linux − https://sourceforge.net/projects/ OS X − https://sourceforge.net/projects/ Using the installer on Windows is a completely wizard based installation. All you need to provide is an administrator access and the location of the installation directory which is “c:xampp” by default. To install XAMPP on Linux, use the following steps − Step 1 − Change the permissions to the installer − chmod 755 xampp-linux-*-installer.run Run the installer − sudo ./xampp-linux-*-installer.run XAMPP is now installed below the “/opt/lamp” directory. Step 2 − To start XAMPP simply call this command − sudo /opt/lampp/lampp start You should now see something like this on your screen − Starting XAMPP … LAMPP: Starting Apache… LAMPP: Starting MySQL… LAMPP started. Ready. Apache and MySQL are running. You can also use a graphical tool to manage your servers easily. You can start this tool with the following commands − cd /opt/lampp sudo ./manager-linux.run (or manager-linux-x64.run) Step 3 − To stop XAMPP simply call this command − sudo /opt/lampp/lampp stop You should now see something like this on your screen − Stopping XAMPP … LAMPP: Stopping Apache… LAMPP: Stopping MySQL… LAMPP stopped. Also, note that there is a graphical tool that you can use to start/stop your servers easily. You can start this tool with the following commands − cd /opt/lampp sudo ./manager-linux.run (or manager-linux-x64.run) If you are using OS X, follow these steps − To start the installation, Open the DMG-Image, and double-click the image to start the installation process. To start XAMPP simply open XAMPP Control and start Apache, MySQL and ProFTPD. The name of the XAMPP Control is “manager-osx”. To stop XAMPP simply open XAMPP Control and stop the servers. The name of the XAMPP Control is “manager-osx”. The XAMPP control panel is a GUI tool from which the Apache server, and MySQL can be easily started and stopped. Press the Admin button after starting the Apache module. The XAMPP homepage appears like the one shown below − PHP Parser Installation Before you proceed it is important to make sure that you have proper environment setup on your machine to develop your web programs using PHP. Type the following address into your browser”s address box. http://127.0.0.1/info.php If this displays a page showing your PHP installation related information then it means you have PHP and Webserver installed properly. Otherwise you have to follow given procedure to install PHP on your computer. This section will guide you to install and configure PHP over the following four platforms − PHP Installation on Linux or Unix with Apache PHP Installation on Mac OS X with Apache PHP Installation on Windows NT/2000/XP with IIS PHP Installation on Windows NT/2000/XP with Apache Apache Configuration If you are using Apache as a Web Server then this section will guide you to edit Apache Configuration Files. Just Check it here − PHP Configuration in Apache Server PHP.INI File Configuration The PHP configuration file, php.ini, is the final and most immediate way to affect PHP”s functionality. Just Check it here − PHP.INI File Configuration Windows IIS Configuration To configure IIS on your Windows machine you can refer your IIS Reference Manual shipped along with IIS. You now have a complete

PHP – File Include ”; Previous Next The include statement in PHP is similar to the import statement in Java or Python, and #include directive in C/C++. However, there is a slight difference in the way the include statement works in PHP. The Java/Python import or #include in C/C++ only loads one or more language constructs such as the functions or classes defined in one file into the current file. In contrast, the include statement in PHP brings in everything in another file into the existing PHP script. It may be a PHP code, a text file, HTML markup, etc. The “include” Statement in PHP Here is a typical example of how the include statement works in PHP − myfile.php <?php # some PHP code ?> test.php <?php include ”myfile.php”; # PHP script in test.php ?> The include keyword in PHP is very handy, especially when you need to use the same PHP code (function or class) or HTML markup across multiple PHP scripts in a project. A case in point is the creation of a menu that should appear across all pages of a web application. Suppose you want to create a common menu for your website. Then, create a file “menu.php” with the following content. <a href=”http://www.tutorialspoint.com/index.htm”>Home</a> – <a href=”http://www.tutorialspoint.com/ebxml”>ebXML</a> – <a href=”http://www.tutorialspoint.com/ajax”>AJAX</a> – <a href=”http://www.tutorialspoint.com/perl”>PERL</a> <br /> Now create as many pages as you like and include this file to create the header. For example, now your “test.php” file can have the following content − <html> <body> <?php include(“menu.php”); ?> <p>This is an example to show how to include PHP file!</p> </body> </html> Both the files are assumed to be present in the document root folder of the XAMPP server. Visit http://localhost/test.php URL. It will produce the following output − When PHP parser encounters the include keyword, it tries to find the specified file in the same directory from which the current script is being executed. If not found, the directories in the “include_path” setting of “php.ini” are searched. When a file is included, the code it contains inherits the variable scope of the line on which the include occurs. Any variables available at that line in the calling file will be available within the called file, from that point forward. However, all functions and classes defined in the included file have the global scope. Example In the following example, we have a “myname.php” script with two variables declared in it. It is included in another script test.php. The variables are loaded in the global scope. myname.php <?php $color = ”green”; $fruit = ”apple”; ?> test.php <?php include “myname.php”; echo “<h2>$fname $lname</h2>”; ?> When the browser visits http://localhost/test.php, it shows − Ravi Teja However, if the file is included inside a function, the variables are a part of the local scope of the function only. myname.php <?php $color = ”green”; $fruit = ”apple”; ?> test.php <?php function showname() { include “myname.php”; } echo “<h2>$fname $lname</h2>”; ?> Now when the browser visits http://localhost/test.php, it shows undefined variable warnings − Warning: Undefined variable $fname in C:xampphtdocstest.php on line 7 Warning: Undefined variable $lname in C:xampphtdocstest.php on line 7 include_once statement Just like include, PHP also has the “include_once” keyword. The only difference is that if the code from a file has already been included, it will not be included again, and “include_once” returns true. As the name suggests, the file will be included just once. “include_once” may be used in cases where the same file might be included and evaluated more than once during a particular execution of a script, so it can help avoid problems such as function redefinitions, variable value reassignments, etc. PHP – Include vs Require The require keyword in PHP is quite similar to the include keyword. The difference between the two is that, upon failure require will produce a fatal E_COMPILE_ERROR level error. In other words, require will halt the script, whereas include only emits a warning (E_WARNING) which allows the script to continue. require_once keyword The “require_once” keyword is similar to require with a subtle difference. If you are using “require_once”, then PHP will check if the file has already been included, and if so, then the same file it will not be included again. Print Page Previous Next Advertisements ”;