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Some useful functions for manipulating array

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Function Explanation Example sizeof($arr) This function returns the number of elements in an array.Use this function to find out how many elements an array contains; this information is most commonly used to initialize a loop counter when processing the array. Code: $data = array("red", "green", "blue");echo "Array has " . sizeof($data) . " elements"; ?>Output: Array has 3 elements array_values($arr) This function accepts a PHP array and returns a new array containing only its values (not its keys). Its counterpart is the array_keys() function.Use this function to retrieve all the values from an associative array. Code: $data = array("hero" => "Holmes", "villain" => "Moriarty"); print_r(array_values($data)); ?>Output: Array ( [0] => Holmes [1] => Moriarty ) array_keys($arr) This function accepts a PHP array and returns a new array containing only its key...
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Differences between echo, print and print_r in PHP

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echo : Outputs one or more strings. And echo is not a function, but a language construct. echo has a void return type.echo is not actually a function (it is a language construct), so you are not required to use parentheses with it. echo (unlike some other language constructs) does not behave like a function, so it cannot always be used in the context of a function. Additionally, if you want to pass more than one parameter to echo, the parameters must not be enclosed within parentheses. For example: <?php   echo “Hello World”; ?> echo also has a shortcut syntax, where you can immediately follow the opening tag with an equals sign. This short syntax only works with the short_open_tag configuration setting enabled. For example: My name is <?=$name; ?>. Note: However, short tags are discouraged to use in modern versions on PHP.. print: print is not actually a real function (it is a language construct) so you are not required to use parentheses with its argument list. ...
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PHP File Upload

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Create an Upload-File Form To allow users to upload files from a form can be very useful. Look at the following HTML form for uploading files: <html> <body> <form action=”upload_file.php” method=”post” enctype=”multipart/form-data”> <label for=”file”>Filename:</label> <input type=”file” name=”file” id=”file” /> <br /> <input type=”submit” name=”submit” value=”Submit” /> </form> </body> </html> Notice the following about the HTML form above: The enctype attribute of the <form> tag specifies which content-type to use when submitting the form. “multipart/form-data” is used when a form requires binary data, like the contents of a file, to be uploaded The type=”file” attribute of the <input> tag specifies that the input should be processed as a file. For example, when viewed in a browser, there will be a browse-button next to the input field Note: Allowing users to upload files is a big security risk. Only permit...
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PHP File

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Opening a File The fopen() function is used to open files in PHP. The first parameter of this function contains the name of the file to be opened and the second parameter specifies in which mode the file should be opened: <html> <body> <?php $file=fopen("welcome.txt","r"); ?> </body> </html> Note: If the fopen() function is unable to open the specified file, it returns 0 (false). Example The following example generates a message if the fopen() function is unable to open the specified file: <html> <body> <?php $file=fopen("welcome.txt","r") or exit("Unable to open file!"); ?> </body> </html> Modes Description r Read only. Starts at the beginning of the file r+ Read/Write. Starts at the beginning of the file w Write only. Opens and clears the contents of file; or creates a new file if it doesn't exist w+ Read/Write. Opens and clears the content...
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PHP Include

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Server Side Includes (SSI) You can insert the content of one PHP file into another PHP file before the server executes it, with the include() or require() function. The two functions are identical in every way, except how they handle errors:     include() generates a warning, but the script will continue execution     require() generates a fatal error, and the script will stop These two functions are used to create functions, headers, footers, or elements that will be reused on multiple pages. Server side includes saves a lot of work. This means that you can create a standard header, footer, or menu file for all your web pages. When the header needs to be updated, you can only update the include file, or when you add a new page to your site, you can simply change the menu file (instead of updating the links on all your web pages). PHP include() Function The include() function takes all the content in a specified file and includes it in the...
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