There are two types of comments in PHP, single line comments, and multi-line comments.
Single-line comments are started with
// and continue until a new line.
$variable = 2; // This is a single-line comment
Multi-line comments start with
/* and continue until
$var1 = 4.5; /* This is a multi-line comment */ $var2 = 6.7;
Printing to the current HTML page is an easy way of debugging, as long as you don’t care that debug data momentarily appears on your website (e.g. your running on a test server, or just that you don’t care). Be careful at leaking sensitive information to the public via this method.
echo is a simple command which outputs text back to the HTML page, from within a PHP code block (something surrounded by
You can use the function
get_defined_vars() to return an array of all defined variables in the scope of where this function is called. Note that this returns all variables, no matter whether they were defined by the system or the user.
print_r() converts almost any object into a human-readable text output.
You can convert almost any object into a string using the function
serialize(). This creates a text-representation of the object which can be converted back into an exact replica of the object at a later date.
Opening/Closing PHP In Html
A PHP code block in the middle of an HTML page is opened with <?php and closed with ?>.
/* To open */ <?php /* php code goes here */ /* To close */ ?>
Getting The Current Path
Commonly, you will find yourself wanting to find the current path of the php script you are running. The universal way to do this, which even works for included files, is to use:
If you want to just get the current directory, you can use the dirname() function to parse the
__FILE__ variable as follows:
$dir = realpath(dirname(__FILE__));
__FILE__ all the way up the the string
public_html. You can use the
preg() function to do this as follows (note this function also replaces and
/, which is a good thing to do to make sure paths are in NIX notation.
To get the current file URL, which won’t work for included files (it will return the URL of the file it was included from), use:
<?php echo $_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF']; ?> // This will return "mysite.com/php-file.php"
To get the current URL, including any passed in parameters (called the URI), use:
<?php echo $_SERVER['HTTP_HOST'].$_SERVER["REQUEST_URI"]; ?> // This will return "mysite.com/php-file.php?var1=abc&var2=def"