The strtotime function is used to convert a date in various formats to a timestamp. However its behaviour is different based on architecture it is running on, whether 32bit or 64bit. Lets take a few examples : In 64 bit environment desktop:~$ php -a Interactive shell php > echo strtotime("0000-00-00 00:00:00"); -62170005200 php > echo… Read More »
If a file is to be saved in at path /var/www/a/b/c/d/abc.zip where the directory c and d dont exist then the directories have to created. Here is a function that uses recursion to check for directories in a path and create them if they do not exist : /** Make a nested path , creating… Read More »
Php from command line PHP scripts are usually opened in a web browser. But they can be run from command line or terminal as well. The syntax to run a script from commandline is very much similar to python or perl. php /path/to/script/index.php Inside a script it might be necessary to test if it is… Read More »
Resizing images Web applications often need to work with images like pictures of users or photos etc. So the need to resize images comes up when creating thumbnails for example or compressing images for storage. The default library to handle image operations in php is GD. It can be used to resize images. GD vs… Read More »
System load System load is a measure of how busy the system is running the processes. Higher system load simply means more processes are running and more are waiting to be run. When coding php applications, it sometimes is useful or necessary to find the current load on the server/system. For example if you want… Read More »
Path Info Urls When using path info data , the urls of codeignitor apps or your custom mvc frameworks looks something like this example.com/index.php/controller/method/param1/param2 or example.com/controller/method/param1/param2 The path info data can be used to specify which class and method should be invoked on server application. Forward slash in parameter Sometimes it might so happen that… Read More »
The PATH-INFO is the extra path data that follows the name of a script (or servlet) in the URL. Its different from query string. Here is a classic example: https://www.examples.com/index.php/some/path?a=b Now, over here we are actually invoking the script index.php only. However also providing some path-info data “/some/path”, which is then followed by the query… Read More »
To go back to the previous page the superglobal variable $_SERVER can be used. $_SERVER[‘HTTP_REFERER’] has the link to the previous page. So to redirect simply : // Method to go to previous page function goback() { header("Location: {$_SERVER['HTTP_REFERER']}"); exit; } goback();
The numerical system used in India differs from the Western system in terms of the placement of the thousands separator. Example : Number -> 1000000 Indian System -> 10,00,000 (Ten Lakh) Western System -> 1,000,000 (1 Million) While echoing numbers in PHP it is possible to format numbers with such separators using functions like number_format…. Read More »
Ip to Location Many applications need to get information about the geographical location of the user/visitor on their websites. This can be done in many ways. There are online services like ipinfodb and geoio that provide web based api to get the geolocation information about a given ip address. Services like Maxmind geoip provide free… Read More »
Parsing dates Most php applications need to parse dates and convert them to timestamps for example. Parsing is also necessary to convert the date into a more standard format like yyyy-mm-dd which can be stored in a database like mysql. Mysql database stores dates in the format yyyy-mm-dd like 2009-04-15. However humans are more used… Read More »
In a previous post we learnt how to inside php. In this example the same zip file would be used to restore the database. Code // Function to restore from a file function restore($path) { $f = fopen('restore/temp.sql' , 'w+'); if(!$f) { echo "Error While Restoring Database"; return; } $zip = new ZipArchive(); if ($zip->open($path)… Read More »
Many php applications prefer to backup the mysql database from within the application and save it as an archive. The mysqldump commandline utility can be used to perform this function of backing up a mysql database as sql file. The command would be like this : mysqldump –user=$username –password=$password –opt $db_name > $dir/backup.sql The above… Read More »
The following function will parse a given text and convert all the urls into links. It does this using regular expressions. It converts email addresses to mailto links as well. Code function parse_links($str) { $str = str_replace('www.', 'http://www.', $str); $str = preg_replace('|http://([a-zA-Z0-9-./]+)|', '<a href="http://$1">$1</a>', $str); $str = preg_replace('/(([a-z0-9+_-]+)(.[a-z0-9+_-]+)*@([a-z0-9-]+.)+[a-z]{2,6})/', '<a href="mailto:$1">$1</a>', $str); return $str; }
Automatic Running In a web application there are many cases, when a certain piece of code or script needs to run automatically in the background to perform certain tasks, without the need of any user to start it. Like scraping, extracting or crawling data from web or perform some regular tasks like sending emails, system… Read More »
The PHP function set_time_limit is used to set a time limit on the maximum execution time of a script. But if the script has socket operations using fsockopen , fread and fwrite or even CURL then the set_time_limit may not appear to have any effect on the scripts timelimit or timeout. Again if safe mode… Read More »
Client IP address Php applications are mostly web based and often need to get the ip address of the user who is connecting to the application. Ip address is required for various logging purpose, geolocation service etc. The most common way to get the ip address of a remote user is by using the superglobal… Read More »
Till recently most of my php scripts were working fine on the servers with instantaneous outputs as and when a echo statement was encountered. Output in Chunks One issue that popped a lot on localhost was that of chunky outputs; that is the outputs of big scripts came out in chunks rather than smoothly with… Read More »
Remote login with CURL The curl extension of php can be used to open remote webpages by both GET and POST methods. There are many situations when you need a php script to login into a website and open a certain page. For example when you are writing a bot or web scraper. To login… Read More »
Database applications written in php often need to export data for reporting purpose. A popular export format is excel. Excel is a spreadsheet that lays out data in a grid format. Excel itself is a microsoft proprietory format. There are many libraries available for php like Spreadsheet_Excel_Writer pear package etc that can do the job…. Read More »