PHP

To redirect the current page to a different location you use the header() function in the following way:

header("http://www.hashbangcode.com");

You can use this function when you want to point the user to a different page. If you are writing a login script then this function would be useful to show the user a certain page depending on them entering the correct user information.

If you are querying a database you should get into the habit of sanitising your input, even if it's not coming from users at the moment it might do in the future. SQL injection attacks are all too common and they can be easily prevented.

The addslashes() function takes a string as the input and returns a string with backslashes before all characters that required quoting in database queries. The characters it acts on are quote, double quote, backslash and NUL (or a NULL byte). Magic quotes runs addslashes() on all COOKIE, GET and POST data. The important thing is not to use addslashes() and magic quotes on the same string as everything will be double escaped.

Use the get_magic_quotes_gpc() function to see if magic quotes is enabled. If it isn't then use the PHP function addslashes() to do the same thing. Use this function if you have any user input in order to sanitise anything that you are about to send to a database.

Those of you who have coded in PHP must have looked at the PHP website at some point, even if it was just to down load the latest version, or to look up a function reference.

What most people don't realise is that there is a really easy way to go straight to the page that you want without having to mess around with the tetchy search engine on the PHP site.

Lets say you wanted to know about the function phpinfo(). This is a debugging function that displays everything you could possible imagine about the PHP environment and is usually used by people who are just starting out with the language as it prints a lot of stuff to the screen.

To look at the reference for the phpinfo() function you could go to the following URL.

The following mode function will return the most commonly occurring value from an array of values, also called the mode. If just the array is used then only the most commonly occurring value will be returned. The second parameter can be used to return an array containing the mode and the number of times that this value occurs in the array.

Reading or writing a file using PHP is quite a common practice, but it can often fall cause programs to fall flat on their face if the proper user privileges are not in place. Although this is not a problem on Windows machines due to the lack of a proper security model, but on Linux machines you need to make sure your scripts can run with the correct permissions.

First you must determine what the name of the user and group is. On OS X the default is "www" for both user and group. If you are using Apache then the user and group information is kept in the http.conf file. Look for a couple of lines that look like this, this is the default settings for Apache 2.2.

Here is a function to create a group of radio buttons in a HTML form. The three parameters are:

1. $name : The name of the radio group.
2. $options : An associative array of items to be included in the group of radio buttons.
3. $default : The default value of the radio buttons.

function createRadio($name,$options,$default=''){
  $name = htmlentities($name);
  $html = '';
  foreach($options as $value=>$label){
    $value = htmlentities($value);
    $html .= '<input type="radio" ';
    if($value == $default){
      $html .= ' checked="checked" ';
    };
    $html .= ' name="'.$name.'" value="'.$value.'" />'.$label.'<br />'."\n";
  };
  return $html;
}

You can call the function in the following way:

It is very easy to break a program with a simple typo. Instead of typing == when comparing two values you type = and actually assign a variable. This is an easy way to introduce a bug as you will not always notice it until your program doesn't work. There is an easy way of avoiding this.

By using the following syntax:

if(100 == $score){ }

Instead of the usual format:

It is very easy to break a program with a simple typo. Instead of typing == when comparing two values you type = and actually assign a variable. This is an easy way to introduce a bug as you will not always notice it until your program doesn't work. There is an easy way of avoiding this.

By using the following syntax:

if(100 == $score){ }

Instead of the usual format:

To find if a number is odd or even you can use one of two operators.

The modulo operator (% in PHP) can be used to calculate the remainder of the value divided by 2. This gives a value of 0 for even numbers and a value of 1 for odd numbers. This can be used in an if statement as 0 will equate to false and 1 will equate to true.

$value = 10;
if ($value % 2) {
  echo '$value is odd';
} else {
  echo '$value is even';
}

The second method is to use the & (AND) operator with the number 1. This will perform a bitwise calculation on the number and 1, returning 0 if the number is even and 1 if the number is false. So using the same if statement logic as before we can write.

To round a number in PHP you can use one of three functions, these are round(), ceil() and floor(). All of these functions take number as the input and will round the value depending on the function used.

To round to the closest integer use the round() function.

round(4.4);  // returns 4

To round down to the nearest whole number use the floor() function.

floor(4.4);  // returns 4

To round up to the nearest whole number use the ceil() function.

The is_numeric() function in PHP can be used to see if a number contained in a string is numeric. The function returns true is the variable can be parsed into a string, otherwise it returns false. Here are some examples:

is_numeric('five')  // returns false
is_numeric(123); // returns true
is_numeric('123'); //  returns true
is_numeric(-123); //  returns true
is_numeric('-123'); //  returns true
is_numeric('123.4'); //  returns true
is_numeric('1,234'); //  returns false

Notice that if your number has a thousand separator in it the function will return false. In this case you need to use the str_replace() function to strip out the commas before passing the value into is_numeric(0).