Tag: tip

Quick Tip: getcwd() for Contents of Current Directory

The getcwd() function is short for ‘GET Current Working Directory’. This can easily be combined with the scandir() function which returns an array of all the files and directories inside the specified directory. This tip was excluded from the book as an oversight.
 
A quick way to get a list of all the contents of the current directory is to use the following code:

function preprint($arr){
  echo '< pre>'.print_r($arr).'< /pre>';
}
$array = scandir(getcwd());
preprint($array); // nicely formatted display of the array

 
Of course, you can skip the print/echo portion if you don’t wish to display the contents and just use the array to perform other checks, but you get the idea.

PHP & Ampersand: Passing by Reference

The following PHP Reference excerpt is from pages 20-21.

& – Pass by Reference

References allow two variables to refer to the same content. In other words, a variable points to its content (rather than becoming that content). Passing by reference allows two variables to point to the same content under different names. The ampersand ( & ) is placed before the variable to be referenced.

Examples:

$a = 1;
$b = &$a; // $b references the same value as $a, currently 1
$b = $b + 1; // 1 is added to $b, which effects $a the same way
echo "b is equal to $b, and a is equal to $a";
b is equal to 2, and a is equal to 2



Use this for functions when you wish to simply alter the original variable and return it again to the same variable name with its new value assigned.

function add(&$var){ // The & is before the argument $var
$var++;
}
$a = 1;
$b = 10;
add($a);
echo "a is $a,";
add($b);
echo " a is $a, and b is $b"; // Note: $a and $b are NOT referenced
a is 2, a is 2, and b is 11

You can also do this to alter an array with foreach:

$array = array(1,2,3,4);
foreach ($array as &$value){
$value = $value + 10;
}
unset ($value); // Must be included, $value remains after foreach loop
print_r($array);
Array ( [0] => 11 [1] => 12 [2] => 13 [3] => 14 )

What tricks do you have for using the ampersand in PHP to pass by reference?
Leave them in the comments below!